# Posts by Elle

Total # Posts: 188

**Trig**

Verify the identity. 1/(tanx-secx) + 1/(tanx+secx) = -2tanx

**Math**

A club consists of 8 seniors, 7 juniors, and 4 sophomores. A subcommittee consisting of 3 seniors, 2 juniors, and 1 sophomore will be chosen. How many different such subcommittees are there?

**math**

Part 1 : Store equipment is purchased on January 1, 2002 at a cost of $14,000 and $1,000 was spent on its installation. The depreciation is written-off at 10% on the original cost every year. The books are closed on December 31, every year. Instructions: Prepare a Depreciation...

**Pharmacy Calculaions**

I can't get this right! Please help... Based on the formula below, what quantities of each are needed to make 180 ml of this lotion? Benzyl Benzoate 250 ml Triethanolamine 5 ml Oleic Acid 20 ml Purified water to make 1000 ml

**Physics**

Two objects are connected by a string with a mass less, friction less pulley. The coefficient of friction is .298. The block on the table is 4 kg. What must the mass of the hanging block be so that the block on the table will move with a constant speed?

**Physics**

A 1.1 kg lizard lies on a flat rock tilted. A person decides to tilt the rock hoping that the lizard falls off. The rock is tilted at an angle of 15 degrees with respect to the horizontal. The coefficient between the rock and the lizard is .16. What is the acceleration of the ...

**World History**

What factor led the English to attempt to kill off entire Native American peoples? A. Native Americans provided a good labor source for the Spanish. B. Native Americans had vast wealth to exploit for tribute. C. The Native Americans' large populations were a direct threat...

**Geometry**

EAD

**organic chem**

if sulfuric acid was not added to isopentyl alcohol how would that affect the results

**Chemistry**

A coffee-cup calorimeter initially contains 125 g water at 24.2 degrees celsius. Potassium bromide (10.5 g), also at 24.2 degree celsius, is added to the water, and after the KBr dissolves, the final temperature is 21.1 degrees celsius. Calculate the enthalpy change for ...

**Biology**

In ion exchange chromatography, why do you have to be careful not to disturb the resin bed or let air enter the resin bed? I get that it disturbs resolution.. but I'm not sure exactly what to say.

**Chemistry**

A portable electric water heater transfers 255 watts (W) of power to 5.5 L of water, where 1 W = 1 J/s. How much time (in minutes) will it take for the water heater to heat the 5.5 L of water from 25 degrees celsius to 42 degrees celsius? (Assume that the water has a density ...

**Chemistry**

25.0 mL of ethanol (density = 0.789 g/mL) initially at 7.0 degrees celsius is mixed with 35.0 mL of water (density = 1.0 g/mL) initially at 25.3 degrees celsius in an insulated beaker. Assuming that no heat is lost, what is the final temperature of the mixture?

**Algebra**

1. First you need to find the slope of the original line you are given which is 3x + y = 6. The slope is -A/B so it is -3/1 or just -3, m = -3. 2. The slope of a line perpendicular is the negative reciprocal so the slope of the line perpendicular to the given line is 1/3. 3. ...

**chemistry**

Determine the theoretical and percent yield of hydrogen gas is 36 g of water undergoes electrolysis to produce hydrogen and oxygen and 3.8 g of hydrogen is collected.

**Chemistry**

How would you make 100mL of tartrate buffer, pH 3.5, from 0.100 M tartaric acid, 1M NaOH and deionized and distilled H2O? You need to consider the ionization of two the two acidic groups separately.

**Chemisty**

16.72g of sodium acetate trihydride (MW=136 g/mol) is dissolved in 100mL water. To this, 4.00g glacial acetic acid (Ka=2.2x10-5, MW=60.0 g/mol) is added, and distilled water is added to to the 500mL mark. Find the final pH and the molar concentration of the buffer.

**Chemistry**

How would you make 100mL of tartrate buffer, pH 3.5, from 0.100 M tartaric acid, 1M NaOH and deionized and distilled H2O? You need to consider the ionization of two the two acidic groups separately.

**Geometry**

PQR is congruent to DJE. complete the statement below PR is congruent to __, DJ is congruent to __ angle E is congruent to __ 1) PR is congruent to PQ, DJ is congruent to PQ, angle E is congruent to angle R 2) PR is congruent to DE, DJ is congruent to DR, angle E is congruent ...

**trig**

You are sky diving and are trying to land on a target with a radius of 15 m. You land 10 m west and 10 m north of the center of the target. a. Write an inequality to describe the region inside the target area. b. Do you land within the target area? c. If another skydiver lands...

**Physics help!!**

A team of dogs drags a 150 kg sled 1.39 km over a horizontal surface at a constant speed. The coeﬃcient of friction between the sled and the snow is 0.236. The acceleration of gravity is 9.8 m/s^2. Find the work done by the dogs. Also, What is the energy lost due to ...

**Physics**

Another quick question, what is the ratio K2/K1 of their kinetic energies. Is, it just dividing the second bullet's KE to the first?

**Physics**

I see! Thank you!

**Physics**

Two bullets have masses of 2.4 g and 5.2 g, respectively. Each is ﬁred with a speed of 37.0 m/s. a) What is the kinetic energy of the ﬁrst bullet? b) What is the kinetic energy of the second bullet? I initially used KE=1/2MV^2 and got 1642.8 J, but got it wrong. ...

**Physics help!!**

i got the magnitude i still don't get tan A = Fy/Fx can you explain thoroughly?

**Physics help!!**

A crate is pulled to the right with a force of 80 N, to the left with a force of 125.8 N, upward with a force of 615.4 N, and downward with a force of 248 N. Net external force in the x direction: -45.8 Net external force in the y direction: 367.4 N how do i find the magnitude...

**Physics.. please help!!!!!**

A crate is pulled to the right with a force of 80 N, to the left with a force of 125.8 N, upward with a force of 615.4 N, and downward with a force of 248 N. What is the net external force in the x direction? y direction?? Also.... What is the magnitude of the net external ...

**Physics.. please help!!!!!**

A ball of mass 0.4 kg, initially at rest, is kicked directly toward a fence from a point 20 m away, as shown below. The velocity of the ball as it leaves the kicker’s foot is 16 m/s at angle of 46◦ above the horizontal. The top of the fence is 4 m high. The ball ...

**Physics.. please help!!!!!**

A person walks 28.2◦ north of east for 3.33 km. Another person walks due north, then due east to arrive at the same location. How far due north would this person walk? How far would this person walk due east?

**Trig!**

The identities cos(a-b)=cos(a)cos(b)sin(a)sin(b) and sin(a-b)=sin(a)cos(b)-cos(a)sin(b) are occasionally useful. Justify them. One method is to use rotation matricies. Another method is to use the established identities for cos(a+b) and sin (a+b).

**chemistry**

If the amount of mercury in a polluted lake is 0.40 ug/mL, what is the total mass of mercury in the lake? (The lake has a surface area of 100 mi squared and an average depth of 25 ft).

**algebra 1**

I was given this interesting problem: The length of a rectangle is 6 feet longer than its width. The perimeter is less than 48 feet. Write a mathematical expression for the width of the rectangle. How do I go about doing this?

**physics**

A car can go from 0 to 85 km/h in 10 s. If the engine delivered twice the power, how many seconds would it take?

**chemistry**

How many grams are required to make 1.5 L of 3.0 M hydrochloric acid (HCl) solution?

**chemistry**

How many grams are required to make 1.5 L of 3.0 M hydrochloric acid (HCl) solution?

**physics**

FN=mv^2/r

**physics**

how many revolutions per minute would a 15 m ferris wheel need to make for passengers to feel weightless at the top?

**3rd grade**

Could you divide 14 shirts into equal groups

**Chemistry**

Hydrogen and oxygen gas combine explosively to produce water. Write a balanced chemical equation for this process. If 10 mol of hydrogen reacted with oxygen, what volume of liquid water could be produced?

**Algebra 2**

the charge for a one day rental of a car from Hawks car rental agency is $24 plus 15 cents for each mile driven. a) If sarah drives 85 miles in one day, how much is the charge? b) If a one day rental cost Sarah $42, how far did she drive?

**PRE-CALC**

I got a different answer than all of you guys :P HINT: To actually visualize the problem, draw it out! :) Obviously the dimensions of the painting are: w and 3+w We know that the frame is 12 in wide, aka 1 ft wide. And we also are given that the total area of the painting and ...

**Math values**

The value of cos^-1(-(sqrt3)/2) is what?

**Math**

Lee has two tests to study for: Chemistry and French. She plans to study for up to 13h in total. She will spend at least 4 hours studying Chemistry and up to 6 hours studying French. Let x represent the number of hours she will spend studying Chemistry, and y the number of ...

**Healthcare Management**

What are the most important functions of health information management? (thank you in advance for your help)

**Physics**

A satellite has an orbit with pedigree 175 km and apogee 181,200 km. What is the period of the orbit? >>I'm not sure what the associated equation is. I tried the problem using the average radius in the period equation but it didn't work. Please help!

**Math**

How many different functions are there from a set with 10 elements to sets with the following numbers of elements? a) 2 b) 3 c) 4 d) 5

**Math**

How many different functions are there from a set with 10 elements to sets with the following numbers of elements? a) 2 b) 3 c) 4 d) 5

**physics**

A car engine accelerates at a constant rate from 170 rpm to 3050 rpm in 7 seconds. I have found that at t=0, the angular velocity (omega)=17.8 rad/s, the angular acceleration (alpha)= 43.1 rad/s^2, the tangential acceleration = 7.76 m/s^2, and the centripetal acceleration is ...

**Pre-calculus**

Given the following values for f(t): t : f(t) 3 : -7 6 : 6 9 : 19 12 : 6 15 : -7 18 : 6 a) What is the period, frequency, midline, amplitude, maximum, and minimum? b)Find a possible formula for f(t) c)Find the domain and range of f(t) d)Find a formula for an inverse function ...

**college earth science and astronomy**

Thank you very much bobpursley! This has been quite the challenge to learn without the benefit of a teacher. I want to run my answers past and see if I have calculated correctly. energy= 250 * 2.5 = 625 Calories Then solar energy flux will be 250 *2.5 (625) / 63.6 * 10 (636) ...

**college earth science and astronomy**

This isn't homework as much as I am trying to learn this on my own. I am trying to perform an experiment on solar power. I measured and recorded the volume (V= 250 mL) and mass (M= 250 g) of water in a cup. I then recorded the initial temperature(32 degrees celcius) of the...

**Chemistry**

I had to find the numbers of atoms in 2 Al (NOsubscript 3)subscript 3. I got 16, but the answer in my book is 26. Who is incorret? Thanks!!!

**social studies**

Are you asking about symbols used in ancient writing? If you are, an example is hieroglyphics (don't trust me that I spelled that right). Hope I helped you!

**Another algebra**

Determine the number of positive integers n that satisfy: 1/2 < n/n+1 < 99/101 I don't know how to solve this besides plugging in random numbers, which would take all day. Any other suggestions for a faster way to solve it? Thank you!

**Algebra**

What is the length of the interval of solutions to the inequality 1 ( is less than or equal to) 3-4x (is less than or equal to) 9? I presume that I just plug in numbers for x? The problem is, that all the positive numbers I've tried have made them way less than one, when ...

**math**

Try to make two equations, one for each phone company. First plan: y = .10x + 18 Second plan: y = .15x Try plugging in numbers until the two equations have the same y. If you need anymore explanations, just respond back. Hope I helped!

**Math**

woooow really mature. "yo moma" oh that's so funny...what are we, in third grade? it's "aflyerquacker"

**english**

what should i do if i can't come up with a title for an essay? is it alright for it to be untitled?

**science**

ecologists usually study a specfic populaions of organisms rather than studying the entire species why?

**Physics**

V=k*q/r so for the above equation, there should without square!

**english**

What is the basic plot of Titus by Shakespere? It doesn't have to be detailed. I think it's about the guy who like kills someone and bakes them in the pie? i don't know if i have it right

**inverse function question**

Hey, I'm having trouble fully understanding absolute value graphs and I've been asked find the largest value of a so that f^-1 exists for the function: f: (-efinity,a) --> R where f(x)= logel2x-1l *note: i have used 'l' to represent the straight line ...

**Physics**

Ah, it's right. Thanks alot!

**Physics**

The cable of an elevator of mass M = 1020 kg snaps when the elevator is at rest at one of the floors of a skyscraper. At this point the elevator is a distance d = 18.4 m above a cushioning spring whose spring constant is k = 6500 N/m. A safety device clamps the elevator ...

**Physics**

Um are you saying Wtotal = [(1020)(9.8)-6678] (18.4+x) ?.. In that case, I did the quadratic and got x=17.33m, but still wrong answer :( argg

**Physics**

Wtotal = [(1020)(9.8)-6678] 18.4 = 61051.2J 61051.2J = 1/2 (6500)x^2 x = 4.33m STill wrong :( Help

**Physics**

The cable of an elevator of mass M = 1020 kg snaps when the elevator is at rest at one of the floors of a skyscraper. At this point the elevator is a distance d = 18.4 m above a cushioning spring whose spring constant is k = 6500 N/m. A safety device clamps the elevator ...

**Another binomial distribution question**

hi, i'd also really like some help for another binomial distribution question, i have no idea where to start... the question is: A manufacturer makes 10,000 ball point pens per day and estimates that 400 will be defective. She decides that if a random sample of 10 pens ...

**binomial distribution**

hey, i'd really appreciate some help with this question: A medical treatment is successful 75% of the time. A hospital wishes to treat a group of patients. How many patients should they take so that the probablity that all are cured is 1/10? I know that p=0.75 and q=0.25 ...

**maths**

hey, i would really appreciate some help solving for x when: sin2x=cosx Use the identity sin 2A = 2sinAcosA so: sin 2x = cos x 2sinxcosx - cosx = 0 cosx(2sinx - 1)=0 cosx = 0 or 2sinx=1, yielding sinx=1/2 from cosx=0 and by looking at the cosine graph, we conclude that x=pi/2 ...

**maths**

hi, i'm having trouble with this question: The cost of running a train at a constant speed of v km/h is C=50+v^2/1000 dollars/hour find the time taken for an 800km journey in terms of v.

**differentiation**

hey, i'd really appreciate some help differentiating this equation: t= (4+x^2)^(1/2) /3 + (3-x)/5 so that's four plus x to the power of 2 all to the power of 1/2 all over three plus 3-x divided by five... :P Thankyou. I would rewrite it as t= (1/3)(4+x^2)^(1/2) + 3/5...

**maximum and minimum problems when function unknown**

Hi, can anyone please help me with this problem, i have no idea what to do! The question is: a window frame is in the shape of a semicircle joined to a rectangle. Find the macimum area of a window using 300 cm of framework. i can usually solve these sorts of questions when i&#...

**equations of tangents and normals**

hi, i'd really appreciate some help solving this question! I am completely at loss here :/ The question is to: Find the equation of the normal to y=loge(x+2) which is parallel to the line with equation y+3x-5=0 I am fine at solving these sorts of equations when they give ...

**circular (trigonometric) functions**

hi, i need help solving this trigonometric equation: sinx+3cosx=0 i don't know what to do as i can't just diviide the two to create tanx which is what i have been doing in previous questions... yes, you are on the right track sinx = -3cosx sinx/cosx = -3 tanx = -3 so x...

**exponential and logarithmic graphs question**

hi, i desperately need help solving this question: Find the values of A and k if the general equation of the graph shown is y=Ae^kx where the graph goes through the points (-1,-4) and (-2,-10) do i solve it using simultaneous equations? because i have attempted this yet failed...

**maths help needed!**

Hi, just a short question. How do i find the x intercepts for the equation y=-2x^3+1 ? I tried to let y equal zero but i could only get as far as x^3=1/2 please help! x^3 = 1/2 is correct. There is only ine x-intercept. It is where x = (1/2)^(1/3) which means the cube root of ...

**Econ T/F**

yes, its a true or false question is this a true or false question? Suppose that after a price change, the income effect is zero, but the substitution effect is not. For such a good, the quantity demanded is directly related to its price. oh well I think it is true. hummmm. ...

**Econ T/F**

A consumer with a fixed income buys two goods, X and Y. If her demand for both X and Y are unitary elastic, she must spend an equal amount on each good. take a shot, what do you think, and why? i think false, she doesn't have to spend equal amount?? I agree

**Econ T/F**

If a consumer is in equilibrium and all prices and her income increase by 25%, she will consume less of those goods that she considers inferior. if false, explain why. Take a shot. What does your economic reasoning tell you? Hint. If all prices and income rise by exactly 25%, ...

**economics**

According to a survey of U.S. firms, the advertising elasticity of demand is only about 0.003. Does this indicate that firms spend too much on advertising? It does not indicate too much is being spent. A 100% increase in advertising would translate into a .3% increase in sales...

**maths, please help!**

I need help solving this: 6x^2-x-12=0 I usually could do this yet i have completely forgotten what i need to do seeing as there is a number infront of the x^2 This equation is of the general form a x^2 + bx + c = 0 The solution is always x = [-b +/- sqrt (b^2 - 4ac)]/(2a) = [1...

**calculus**

hi, just wondering on how i should approach differentiating: loge1/(3-x)^5 can i differentiate it as loge(3-x)^5? sorry i meant to write (3-x)^-5 Hmmmm. You are haveing a brain seizure. Watch this: Ln x^-a= - ln x^a= -a ln x Amazing. So loge1/(3-x)^5= -5 ln(3-x) Check my ...

**maths**

hi, i would really appreciate some help on simplifying this question: -2(3e^-x-e^x)(-3e^-x-e^x) could this be simplified as -2(3e^-x-e^x)-(3e^-x-e^x) which would then become (-2-1)(3e^-x-e^x) i feel this isn't right however...

**math**

hi i would really appreciate some help solving this question simultaneously: Find A and B such that x-11/(x+3)(2x-1)= A/x+3 + B/2x-1 Multiply both sides by (x+3)(2x-1) to get rid of the fractions. We end up with this: (x-11) = A(2x-1) + B(x+3) You can solve for A and B more ...

**math**

I need help differentiating this question: 3e^-4x that's three e to the power of negative 4x. when you differentiate, you get: -12e^-4x thanks, but how come it's not -12e^-4x-1, or do i just not minus a one when the power is a co-efficient? Remember, the differential ...

**acids and alkalis**

TOOTH PASTE - Alkali OVE CLEANER - Alkali Soz nufin else maybe some more in a minute!!! gtg Bye XXX

**Geometry?**

I need help with these: Suppose triangleABC ~ triangleJKL with BC = 28, JK = 12, and KL = 42. Find the perimeter of triangleABC if the perimeter of triangleJKL is 72. & Find the scale factor of triangleDEF to triangleXYZ if triangleDEF ~ triangleXYZ, DE=10, XZ=20, and XY=45. ...