Thursday

April 24, 2014

April 24, 2014

Total # Posts: 21,958

**derivatives - oops**

d/dx sinx = cosx

**math**

http://www.wolframalpha.com/input/?i=4x^2+cosx

**math - back to speed**

Reiny is, of course, correct, but given the choice of answers, I went with the assumption that they were just looking for knowledge of the area of the circle. And besides, who said that the flower areas were of any particular shape? Nothing says that the plants around the edge...

**math***1questions*****

pi * 7^2 = 154

**Calculus Help**

log y = log (e^-x) + log cos^2(x) - log(x^2+x+1) log y = -x + 2log cos x - log(x^2+x+1) 1/y y' = -1 - 2tanx - (2x+1)/(x^2+x+1) y' = -(1 + 2tanx + (2x+1)/(x^2+x+1)) * (e^-x cos^2x)/(x^2+x+1) Now, you can massage that for a few more steps, to get something that pleases you

**math**

(20)5/6-5A+11 50/3-5+11 17/3-5A

**math**

so, what number do you have to add to 7 to get 10?

**math, please help!**

1987 is 7/10 of the way from 1980 to 1990 So, what is 7/10 of the way from 8558 to 13807 ?

**Trigonometry - incomplete**

no diagram. Better explain a bit more, the relative positions of A,B,C,D

**AP Calc**

was the answer I gave in the 1st related question below incorrect? If so, do you have any suggestions?

**Math**

14x = 9

**Linear Algebra**

ok 3g^-2 b^2 = 3b^2/g^2 negative exponents are in the denominator 3/g^-2 = 3g^2 So, 3/g^-2 h^3 = 3g^2 h^3 missing parentheses?

**math**

decrease = 60 60/310 = ?

**Algebra**

is 1^1 + 2^2 = (1+2)^2

**Math - eh?**

not familiar with the notation fX(x) and fY(y) partial derivatives?

**algebra**

well, (x+y)^2 - (x-y)^2 = 4xy So, (x-y)^2 = 280^2 - 4*19951

**math**

.005(400^2) - 45(400) + 12000

**Algebra**

w(3w-1) = 30 (3w-10)(w+3) = 0

**physics**

minimal, or nominal? Sine I = P/E, what's 100/120 ?

**Algebra I**

10x - 9y = 46 -10x + 15y = 30 6y = 96 y = 16 now get x from either equation

**Math**

v = Bh where B is the area of the base Since the base is a triangle, B = 1/2 * 4 * 5 Now, since h=8, you can easily see that v=80

**Geometry**

6x-8 + 7x+3 + 3x-7 = 180 x = 12 So, evaluate for each angle, then sort them.

**Math**

((n+21)(3)-9)/5 = 30 n = 32

**PRE-CALC**

Looks like C to me Note that C covers more than just this set.

**Physics**

No work = force * distance since distance=0, no work.

**Science**

how did the discovery of nutrons change the atomic model

**Science**

what type of bond is a metal cation likely to form?

**Trigonometry**

by law of cosines, c^2 = a^2 + b^2 - 2ab cosC Now, having a,b,c and C, use the law of since to get A,B. sinA/a = sinB/b = sinC/c

**solid mensuration**

so, what is it you want to know? Just FWIW, I doubt that the altitude as given is correct.

**chemistry**

2C4H10 + 13O2 -> 10H2O +8CO2

**trigonometry**

oops. Forgot all those hours θ = 2π*5 + 2π/3 = 10π + 2π/3 = 32π/3 For the minute hand, that's the same value as 2π/3 but, θ/12 is now 32π/36 = 8π/9 which affects its trig function values immensely.

**trigonometry**

let the plane of rotation of the minute hand be z=0. So, the location of the tip of the minute hand is (9cosθ,9sinθ,0) Similarly, the location of the tip of the hour hand is (6cos θ/12,6sin θ/12,2) at 5:40 am, θ = 2π/3, so θ/12 = π/18 So...

**math**

(24/40)(340)

**Math**

Hmmm. how about y = -50 + 0.2x You can supply the units.

**College math**

4y = 3+9

**math**

s^2 = r^2 + h^2 = (d/2)^2 + h^2 s^2 = 4^2+9^2 = 16+81 = 97 s = 9.8

**Math - eh?**

I know it's a pain to write clearly, but until you do, the help will be thin on the ground. Sorry, I just can't parse that into a meaningful description of a figure.

**physics**

Hmmm. The way I see it, kinetic energy is lost during her rise up the ramp. So, at the moment of takeoff, her KE is 1/2 mv^2 - 1/2 mgh = m(1/2 * 7.59^2 - 1/2 * 9.8 * 0.741) = 25.17m Now, that means that her speed is then 7.10 m/s The vertical component of that is 5.81 m/s, so ...

**intro to comp**

I see only one OS that can act as a server.

**math**

(4.3 * 1.5) x 10^(-8+9)

**Algebra - typo?**

Before I start figuring, is there a typo in hour 3? All the other hours they sold n/n+1 - 1/n peaches, but that 3/4 instead of 1/4 bothers me.

**Algebra**

Generally FOIL refers only to binomials. For general polynomial multiplication/division, visit calc101.com Over on the right there are links for long multiplication and long division. That should help you understand the details

**algebra**

6a^2 + 15b^5

**Physical Science 9**

what type of bond is a metal cation likely to form?

**AP Calc**

x=e^t and y=t^2-3 dx/dt = e^t dy/dt = 2t dy/dx = (dy/dt)/(dx/dt) = 2t/e^t d^y/dx^2 = d/dt (dy/dx) * dt/dx d/dt(dy/dx) = -2(t-1)/e^t dt/dx = 1/(dx/dt) = 1/e^t d^2y/dx^2 = -2(t-1)/e^2t e^2t is always positive, so y">0 when t<1 Hmmm. From above, y' = 2lnx/x y"...

**Physical Science 9**

how did chadwicks discovery of nutrons change the atomic model

**Physical Science 9**

In an ionoic bond how many valence electrons would an atom have?

**Math**

just work with two at a time, and add up the distances. Do you understand the distance formula?

**math**

always

**Math**

(1/4) / (1/8) = 1/4 * 8/1 = 8/4 = 2 Think of it. 1/8 is half as big as 1/4, so there are two of them in 1/4.

**math**

2/3(6+3x)-7x (4+2x)-7x 4-5x

**Business Algebra**

.045x + .06(20000-x) = 987.50

**math**

r = 169/24

**algebra**

y = 82 + 3/4 x

**algebra**

you mention no equation, but if it is a^8 - a^2b^6 = 0 then a^2(a^6-b^6) = 0 a^2(a^2-b^2)(a^4+a^2b^2+b^4) = 0 so, a=0 or a = ±b or a^2 = (-b^2 ± √(b^4 - 4a^4b^4))/2 = (-b^2 ± b^2√(1-4a^4))/2 = -b^2/2 (1 ± √(1-4a^4))

**Alegbra**

(4.3x1.5) x 10^(-8+9) now just collapse the products

**AP Calc - Damon is, of course, correct.**

Dang! I was figuring the size of the legs, not the altitude. As Emily Latella would say, "Never mind."

**AP Calc - Merge answers**

Damon is right about the quadrant. My integral used the whole ellipse as the solid's base, not just the 1st quadrant. So, adjust the values as needed. However, Damon's triangles are not evaluated with the base as hypotenuse. So, the altitude will be base/√2. It i...

**AP Calc**

when the cross-section has a base of 2y, its height is thus y√2 So, the volume is v = ∫[-a,a] 1/2 bh dx = ∫[0,a] (2y)(y√2) dx = 2√2b^3/a^3 ∫[0,a] (a^2 - x^2)^(3/2) dx now it's just straightforward integration and evaluation

**4th Grade Math**

2/3 3/4 3/5, 4/5 ... any ratio where the less than twice the numerator

**College Algebra**

twice the concentration means half the volume, since the same amount of salt remains. So, we lost half of 16 oz, or ?

**AP Calculus**

Not sure what the "circumscribed" condition means, since any rectangle can be circumscribed. Damon's rectangles contain the approximated sections of curve within them, whatever that means. However, since the other choice of boundaries yields 2(1+e^2+e^4), its abs...

**statistics**

I assume you want two answers,since "all are correct and at least one is wrong" is impossible. P(all correct) = 1/4^6 P(some wrong) = 1 - P(all correct)

**Physics**

Hmmm. What's 92% of 750?

**math**

P = R-C = 4x - (2x+20) = 2x-20 When P=0, x=10

**geometry**

newarea = originalarea * (1/7)(1/7)(1/1)

**Mensuratin**

Rats - mixed up the dimensions. Use (3.14) (.5)^2 (7)

**Mensuratin**

not sure what "1 line" is in volume. Anyway, when you figure out how many ml the bottle holds, divide it by the pen's volume, which is (3.14) (3.5)^2 (0.5) cm^3 (or ml)

**геометрия**

since 600º = 360º+240º, you have cos 240º + sin 240º since 240º = 180º + 60º, you have -cos 60º - sin 60º = -1/2 - √3/2 = -(1+√3)/2

**FIN/370**

4800(1+.09)^10 = 11363.35

**Trigg**

you know that sin^2 + cos^2 = 1, so (x/2)^2 + (y/4)^2 = 1 x^2/4 + y^2/16 = 1

**English**

#1 is the most common usage. It is presumed that you want the glass of water in order to drink it, but the context will make that clear. #3 is much less common, but could mean the same thing. It is likely that English is not the speaker's native language. In Portuguese, fo...

**Math**

Not quite, Fiona. When you finally got an answer, you ought to have done just a sanity check. The average speed was somewhere near 200 mph, and the flew for 7 hours, a distance of 57 mile is ludicrous. since time = distance/speed, and the total time was 7 hours, then we want t...

**Math 117**

if y = f(x), the new shifted function will be y-10 = f(x) now just solve for the new y

**Math**

C = pi*d = pi*20

**Math college level**

well, since your tax bracket has not changed, you will still pay the same percentage. 5220/29000 = 18% So, what is 18% of the new, greater income?

**math**

well, since the equation will be x^2+y^2 = r^2 just plug in your values for x and y, and that will give you the necessary r.

**Math**

pi*(15/2)^2

**Please help!**

f(x-12) shifts the graph right by 12 units. (Now all the x-coordinates are 12 less than they were...) g(x) = f(x-12) = ((x-12)+10)^2 = (x-2)^2

**Calculus**

y = e^x (c1 + c2*x) y' = e^x (c1 + c2 + c2*x) Now plug in the initial conditions to get e^2 (c1 + 2c2) = 0 e^2 (c1 + c2 + 2c2) = 1 Now just solve for c1 and c2

**Maths**

excluding the twins means only 27 people are available. So, C(27,4) is the number of teams possible.

**Calculus**

y = c1 e^-6x + c2 e^x Plug in your boundary conditions, and you get c1 + c2 = 0 c1/e^12 + c2/e^2 = 1 Now just solve for c1 and c2

**AP Calculus**

∫[a,b] x^2 dx = 1/3 x^3 [a,b] = 1/3 (b^3 - a^3) Consider only integer values. Then that will give you a^2 + (a+1)^2 + ... + (b-1)^2 + b^2 Now, we know that n ∑ k^2 = n(n+1)(2n+1)/6 k=1 So, we want sum from a-b = sum from 1-b - sum from 1-a, or b(b+1)(2b+1)/6 - a(a+...

**AP Calculus**

each cross-section has base 2x and altitude x√3 So, we want to add up all those triangles v = ∫[a,3] 1/2 * 2x * x√3 dy = √3 ∫[a,3] x^2 dy But, y = |x| + a y-a |x| (y-a)^2 = x^2 v = √3 ∫[a,3] (y-a)^2 dy and now it's cake, right?

**Trigonometry**

2sinx cosx = cosx cosx(2sinx-1) = 0 so, where do you have cosx = 0 sinx = 1/2 ??

**Calculus Help**

actually, I see I did forget to include a factor of 1/(x^2+x+1) in the first term. Dang! Luckily, it's not my job to fix it!

**Calculus Help**

log y = log (e^-x - xcos^2(x)) - log(x^2+x+1) 1/y y' = (-e^-x - (cos^2 x - 2xcosx*sinx))/(e^x - xcos^2 x) - (2x+1)/(x^2+x+1) y' = (-e^x - cos^2 x + xsin2x) - (2x+1)/(x^2+x+1)^2 If you want to put it all over the common denominator, it gets fairly messy on top.

**mat 116**

(2x)^3 + (2^x)^3 that's a sum of cubes, so (2x + 2^x)((2x)^2 - (2x)(2^x) + (2^x)^2) (2x + 2^x)(4x^2 + 2x*2^x + 2^2x) I'm not sure that's any simpler. Maybe you just wanted 8x^3 + 2^3x ?

**Calc**

no big deal f = ln (ln ln x) f' = 1/(ln ln x) * (1/x * 1/ln x) = 1/(x(lnx)(ln lnx))

**Physical Science 9**

when an electric current is passed through water 2 gasses are formed is this a chemical or physical change

**math**

No genius required. Just use your favorite numerical method to find the root: x^.223 - x^.123 - 1 = 0 x = 92.6740 Newton-Raphson is a likely one for this, since the curve is nice and smooth

**Physical Science 9**

How would you separate a mixture of iron fillings , salt, sand, and wood chips

**Physical Science 9**

when exposed to the same amount of heat for the same amount of time, a 3 g sample of copper will experience a greater temperature change then a 12 g sample of copper due to its smaller what?

**Physical Science 9**

a substance made of two or more elements chemically combined in a set ratio or proportion is called what

**Physical Science 9**

the contents of a can of air freshener are gaseous when sprayed but remain a liquid in the can due to what?

**calculus**

for shells, we need to integrate on y, since the area is rotated about a horizontal line, and the shells have thickness dy v = ∫[1,2] 2πrh dy where r = y-1 and h = x = ln y v = 2π∫[1,2] (y-1)lny dy Just use integration by parts to evaluate it.

**Science**

a substance made of two or more elements chemically combined in a set ratio or proportion is called what

**Science**

when molecules of water vapor in the air come into contact with a cold can of soda they lose energy slow down and form a liquid due to a decrease in what?

**basic college math**

in questions like these it is usually to find where the two deals are equal in cost. Or, equivalently, for how many miles is deal A cheaper than deal B. The cost the same when 25 +.4m = 30 + .25m Now just solve for m

**Science**

do pure substances have different chemical and physical properties?

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