Thursday
April 24, 2014

Posts by STEVE


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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