Thursday

March 5, 2015

March 5, 2015

Total # Posts: 20,652

**Calculus**

-4 cos^3 x^4 sin x^4 (4 x^3) = - 16 x^3 cos^3 x^4 sin x^4 how that is tan x2 whatever that is I can not imagine
*November 6, 2014*

**Math**

log 9 - log 300 2 log 4 + 4 log 3
*November 6, 2014*

**Science**

F2 + F1 = .450 (.750) F2 - F1 = .240 (.750) -------------------------- 2 F2 = .690(.750) etc
*November 6, 2014*

**Physics**

force down = 9.81*12 max friction force = 9.81 * 12 * mu forward force - friction force = m a 15 - 9.81*12 * mu = 12 (.2)
*November 6, 2014*

**Math**

I do not think so I think h = 300 - 16 t^2 she is accelerating DOWN 100 = 300 - 16 t^2 t^2 = 200/16 t = 10 sqrt 2 / 4 = 2.5 sqrt 2
*November 6, 2014*

**Physics easier**

http://outreach.phas.ubc.ca/phys420/p420_04/sean/
*November 6, 2014*

**Hurricane Project for Physics Class**

Physics (hard) http://www.psfc.mit.edu/library1/catalog/online_pubs/iap/iap2013/emanuel.pdf
*November 6, 2014*

**Hurricane Project for Physics Class**

Physics (hard) http://www.psfc.mit.edu/library1/catalog/online_pubs/iap/iap2013/emanuel.pdf
*November 6, 2014*

**Hurricane Project for Physics Class**

Click on hurricane in the upper right corner
*November 6, 2014*

**Hurricane Project for Physics Class**

http://coast.noaa.gov/hurricanes/#app=c64c&88cd-selectedIndex=1
*November 6, 2014*

**Calculus**

no v = w^2 h = (2300/3) h but h = (2300 -w^2)/4w
*November 5, 2014*

**Calculus**

v = w^2 h A = 2300 = w^2 + 4 w h 4 w h = 2300 - w^2 h = (2300 -w^2)/4w so v = w^2 [ (2300 -w^2)/4w ] v = 2300 w/4 - w^3/4 4 dv/dw = 2300 -3 w^2 = 0 for max w^2 = 2300/3 w = 27.7 cm etc
*November 5, 2014*

**Math**

2 w + 2 L = 18 so L = 9-w A = w L = 9 w - w^2 w^2 - 9 w = -A find vertex by completing the square for max A w^2 - 9 w + (9/2)^2 = - (A-81/4) (w -9/2)^2 = - (A-81/4) w = 9/2 for max area by the way that means 2 w = 9 and therefore 2 L = 9 so it is a square with sides = 9/2
*November 5, 2014*

**Physics**

No. To start it moving you must overcome the static friction. After that it gets easier. 648 * .86
*November 5, 2014*

**algebra**

sum of arithmetic series a1 = 1 d = 2 an = a1 + (n-1) d so a700 = a1 +(699)(2) sum = (a1 + a700)/n
*November 5, 2014*

**calculus careful with parentheses**

do you mean what you wrote 7 + 3 x^.5 or do you mean 3 [x+7]^.5 ??????????? anyway (x+1)(derivative of second) + (second) (1)
*November 5, 2014*

**Calculus I**

using T for theta dR/dT = (Vo^2 /9.81) cos2T (note max range when T = 45 degrees :) ) 100 dT/T = 2 dT = .02 T = .02 * pi/6 dR = (Vo^2 /9.81) cos2T dT 100 dR/R = cos 2T dT / sin 2T
*November 5, 2014*

**physics**

m g h = (1/2) m v^2 so h = (1/2) (v^2/g) mass has nothing to do with it
*November 4, 2014*

**RIGHT TRIANGLE TRIG**

You are welcome.
*November 4, 2014*

**RIGHT TRIANGLE TRIG**

sin 65 = h/150 assuming that the string hypotenuse is straight
*November 4, 2014*

**Physics- linear acceleration**

Find out how far the wagon went in 19 seconds d = (1/2) a t^2 = (1/2)(.3)(19)^2 each revolution or 2 pi radians the wheel rolls 2 pi r meters so divide d by (2*pi*.374) to find how many turns then multiply that by 2 pi to get radians (1/2)(.3)(19)^2 /.374
*November 4, 2014*

**Math, Please Help! I don't understand!**

I guess x is right and y is up final x = initial x + change in x final y = initial y + change in y beginning x = -2 moves one right -2 + 1 = -1 beginning y = -5 moves 3 up -5 + 3 = -2 b) (-1 , -2)
*November 4, 2014*

**Algebra**

f(f(x)] = p(px+q) + q f[f(f(x)) = p[p(px+q) + q] + q = p^2(px+q) + pq + q p^3 x + p^2 q + pq + q = 8 x + 21 = (p^3-8)x + p^2 q + pq + q = 21 this can not be a function of x or it would not be constant 21 so p^3-8 = 0 p = 2 4 q + 2q + q = 21 q = 3
*November 4, 2014*

**Algebra**

1. slope = 3 y = 3 x + b so to find b 2 = 0 + b b = 2 y = 3 x + 2 2. same way but slope = -1
*November 4, 2014*

**Physics**

find change in momentum .145(27+32) force = change in momentum/time = change in momentum /(1.5*10^-3 )
*November 4, 2014*

**Physics**

131 * 9.9 .00932 * 618
*November 4, 2014*

**Calculus**

x^2 - 6 = - y vertex on y axis, opens down (sheds water) so just do the right half half A = x y hA = -x (x^2-6) = -x^3 + 6 x dhA/dx = 0 at max = -3 x^2 + 6 x^2 = 2 x = sqrt 2 include left half length along x axis = 2 sqrt 2 if x = sqrt 2 y = 6 - x^2 = 6-2 = 4
*November 4, 2014*

**Calculus**

Oh, well I guess I found your point :) (15/26,5/13)
*November 4, 2014*

**Calculus**

rewrite as y = -(6/4)x + 1/4 line perpendicular has slope +4/6 = +2/3 y = (2/3) x + b we want it through 0, -1 -1 = (2/3) 0 + b b = -1 so y = (2/3) x - 1 where does that hit original line? (2/3) x - 1 = -(3/2) x + 1/4 4 x - 6 = -9 x + 3/2 13 x = 15/2 x = 15/26 then y = 5/13 ...
*November 4, 2014*

**physics**

change in momentum = .001 (300 - 700) time in block = .08/(average speed = .08 / [(700+300)/2] Force = change in momentum/time in block
*November 4, 2014*

**Physics**

F = m a solve for a then v = 0 + a t to get t: d = 3.3 = (1/2) a t^2
*November 4, 2014*

**Physics**

PLEASE CHECK FOR TYPOS slope of the air slope of air WHAT?
*November 4, 2014*

**least to greatest fractions**

6/9 is 2/3 if that is what you are asking. I have no idea what the second and third lines are about 4/40 is 1/10 2/5 is 4/10 maybe 7/10 is next ? 3/7 is 6/14 8/14 is 8/14 5/7 is 10/14 so next would be 12/14 = 6/7
*November 3, 2014*

**math**

y = 5 x + 100 your brother has the sign of the slope wrong
*November 3, 2014*

**Algebra**

q = [ (x+113)/2 ]^1/3 q = [ (137+113)/2 ]^1/3 q = 125^1/3 = 5
*November 3, 2014*

**Math**

-1.4 b = -28 b = 28/1.4 = 20
*November 3, 2014*

**Algebra**

y = x^5 - 1/3 inverse x = y^5 - 1/3 y^5 = x + 1/3 = -31/96 + 32/96 = 1/96 if y^5 = 1/96 then y =1/2.5 = .401
*November 3, 2014*

**Calculus**

cost of x tables = [160-.5(x-250)]x for x>/=250 c = 160 x + 125 x - .5 x^2 c = 285 x - .5 x^2 dc/dx = 285 - x max when x = 285 then c = .5*285^2 = 40,612.50 and c = 0 when x = 0 of course but also when x = 285*2 = 570
*November 3, 2014*

**Algebra**

f^-1(1) = 2 (when y = 1, x = 2) f^-1(2) = 5 f^-1(5) = 3
*November 3, 2014*

**Physics**

F = m a 12.1 = 5.9 a solve for a d = (1/2) a t^2 2.6 = (1/2) a t^2 we know a, solve for t v = a t
*November 3, 2014*

**Algebra**

x = 3 y^3 + 2 y^3 = (x-2)/3 so y = [ (x-2)/3 ]^(1/3) = f-1(x) so [ (x-2)/3 ]^(1/3) = 4 [ (x-2)/3 ] = 64 x - 2 = 192 x = 194
*November 3, 2014*

**algebra**

4 q = 5 * 18 2 q = 5 * 9 q = 45/2 = 22 1/2
*November 3, 2014*

**Algebra**

1,1 6,7 2,7 2,3 7,9 3,9 3,5 3,1 8,7 4,7 4,3 9,6 5,6 1,6 1,2 6,8 2,8 2,4 7,10 3,10 3,6 3,2 this thing is a pretty good vacuum cleaner, keep going until it repeats a point :)
*November 3, 2014*

**Algebra**

if y = x^2 - 2 x f(y) = (x^2-2x)^2 - 2(x^2-2x) = f(f(x)) so x^2-2x = (x^2-2x)^2 - 2(x^2-2x) of course x = zero will do :) let z = x^2 - 2x z = z^2 - 2 z z^2 - 3 z = 0 z (z-3) = 0 so another solution is x^2-2x = 0 = x (x-2 we already have x = 0 so now also have x = 2 and also ...
*November 3, 2014*

**Algebra**

I would have said something like that but have been having fun :) She has an imaginative teacher!
*November 3, 2014*

**Algebra**

y = (3x-7) / (x+1) inverse x = (3y-7) / (y+1) x y + x = 3 y - 7 3 y - x y = x + 7 y (3 - x) = (x+7) y = -(x+7)/(x-3) f^-1(x) = -(x+7)/(x-3)
*November 3, 2014*

**physics**

What you did makes sense to me. I guess we are assuming that the sphere has a very thin wall thickness to get the (2/3) m r^2
*November 3, 2014*

**Math**

(5/6 )24 = 20 pennies 20 / 50 = 2/5
*November 3, 2014*

**Math**

(2/5 )35 = 14 did not go in piggy bank (1/2) 14 = 7
*November 3, 2014*

**trig actually, or maybe vector trig**

4.19 cos 10.4
*November 3, 2014*

**PHYSICS**

lol - the other half of the problem 4.19 sin 10.4
*November 3, 2014*

**Physics**

emf = N d flux /dt emf = 660 B pi r^2 d/dt (sin 2 pi t/T) when t = .024, t/T = 1/8 T = .192 second so emf = -660 (pi r^2) (2 pi/T)B cos (2 pi t/T) now I do not know what "average means. Obviously the average of a cosine function is zero. You might guess they mean ...
*November 3, 2014*

**Physics 11U**

goes up from 2 to 8 or 6 meters do vertical problem v = Vi - g t 0 = Vi - 9.8 t at the top (8meters) so t at top = Vi/9.8 h = 2 + Vi t - 4.9 t^2 at top 8 = 2 + Vi t -(1/2)(9.8) t^2 6 = Vi t -(1/2)(9.8) t^2 6 = Vi^2/9.8 - (1/2) Vi^2/9.8 12 (9.8) = Vi^2 Vi = 10.84 m/s now do the...
*November 3, 2014*

**Math Help!**

well, 30 would be 900 and 28 would be 784 so do my proportion thing again 28 x 30 784 872 900 (872 -784)/ (x-28) = (900-784)/(30-28) x-28 = 2*88/116 x = 28 + about 1.5 or around 29.5 so 30 try calculator sqrt (872) = 29.529
*November 3, 2014*

**math**

speed = distance/time speed1 = 1020/3.30 speed2 = 1020/2.75 so speed2/speed1 = 1020/2.75 / 1020/3.30 = 3.30/2.75
*November 3, 2014*

**Math Help!**

go back and see how I did the earlier one with linear interpolation. It clearly works best when you pick perfect squares above and below the desired answer.
*November 3, 2014*

**Physics**

find induced EMF from 193 *area * dB/dt E = (193)pi (5.5*10^-2)^2 (.908) current = i = E/.241 now find B due to i B = mu N i/2 r = 4 pi*10^-7 (193)(i)/(2*5.5*10^-2)
*November 3, 2014*

**Math Help!**

15 --> 225 14 --> 196 13 --> 169 12 --> 144
*November 3, 2014*

**Math Help!**

x 3 z 4 y 9 14 16 linear interpolate (z - 3)/(14-9) = (4-3)/16-9) z - 3 = (5)(1)/7 z = 3 + 5/7 or a bit over 3.5 so pick 3.7 now use calculator 3.742 :)
*November 3, 2014*

**Physics**

(1/2) m v^2 = 182 m v = 27.6 so m = 27.6/v (1/2) (27.6/v) v^2 = 182 (1/2) (27.6) v = 182 etc
*November 3, 2014*

**Help!-algebra**

agree, c
*November 3, 2014*

**Math Help!**

In other words, Brady is right :)
*November 3, 2014*

**Math Help!**

0.8743 8743 8743 8743 * 10^-4 + 8743 * 10^-8 + 8743 * 10^-12 ...... repeating decimal, infinite geometric series a = 8743 r = 10^-4 sum = a/(1-r) = 8743 /(1 - .0001) =8743/.9999 = 87430000 / 9999 which is a rational number being the quotient of two integers/
*November 3, 2014*

**Physics**

initial mass = 73.5 + .21 initial momentum = (73.5 + .21)(2.97) final momentum is the same = .21 (29.3) + 73.5 v solve for v solve the second part the same way initial momentum = .21*29.3 = (.21+61.5)v
*November 3, 2014*

**physics**

calculate moment of inertia I alpha = change in angular rate/change in time = (34-0)/18 radians/second^2 Theta = (1/2) alpha t^2 Ke = (1/2) I w^2 tangent acceleration at rim = r * alpha radial acceleration = v^2/r = w^2 r where w = (1/2) 34 w (r/2) d = average speed * time but...
*November 3, 2014*

**physics**

actually Ke = (1/2) I w^2
*November 3, 2014*

**Math**

share as many sides as possible. Make it square :)
*November 1, 2014*

**Physics**

By the way, your formula is for the volume of a cylinder, not a sphere. Use (4/3)pi r^3
*November 1, 2014*

**Physics**

Volume of Glass = (4/3) pi (Ro^3 - Ri^3) mass of glass = rho V so 1.71 = 2660 (4/3) pi (Ro^3-Ri^3) so (Ro^3 - Ri^3) = 4.8214*10^-4 Now Archimedes assume rho water = 1000 1000 (4/3)pi Ro^3 = 1.71 solve for Ro^3 go back and get Ri^3 take cube roots :)
*November 1, 2014*

**Statistics**

and here is a calculator for it: http://www.neoprogrammics.com/linear_least_squares_regression/
*November 1, 2014*

**Statistics**

for example: http://mathworld.wolfram.com/LeastSquaresFitting.html
*November 1, 2014*

**Statistics**

I do not have your data. However if you have a bunch of points (x1,y1) , (x2, y2) .... (xn,yn) then you can fit a line of form y = m x + b that "best" fits those points, the criterion being that the sum of the squares of distances from the points to the line is ...
*November 1, 2014*

**AP Calc. AB**

y = 2 x + sin x if there were an inverse it would be x = 2 y + sin y 1 = 2 dy/dx - cos x dy/dx 1 = dy/dx (2-cos x) dy/dx = 1/(2-cos x) at x = 2 dy/dx = 1/(2-cos 2) = 1/(2 +.416) = .41
*November 1, 2014*

**AP Calc. AB**

because it does not pass the vertical line test. for every value of g there are multiple values of x because sin x is the same for many x values.
*November 1, 2014*

**College Chemistry**

370g/[(55.85 x 2) + (13 x 3)] = 2.32 mol Don't you mean 16 * 3 not 13 * 3 ?
*November 1, 2014*

**calculus**

Hey I did a couple. Now you do some.
*October 31, 2014*

**calculus**

at 1, y = 2 at 3, y = 0 dy/dx = -2x + 3 = 0 if x = 3/2 at x = 3/2, y = 2.25 so max at x = 3/2 and min at x = 3
*October 31, 2014*

**calculus**

df(x)/dx = 3 x^2 that is the slope at x = 3 slope = 3*9 = 27 so y = 27 x + b put in point at x = 3 to find b 27 =27 * 3 + b so -54 = b so y = 27 x - 54 at x = 2.7 y = 27 * 2.7 -54 = 18.9 the real answer would be y = 19.7
*October 31, 2014*

**statistics**

http://davidmlane.com/hyperstat/z_table.html
*October 30, 2014*

**Geometry**

yes correct m' = -1/m
*October 30, 2014*

**Social Studies**

Do you really think the former colonists would have won the war if they were a minority in the 13 colonies?
*October 30, 2014*

**Social Studies**

No, it is not a.
*October 30, 2014*

**Social Studies**

I thought I answered :) Looking at the link that Ms. Sue gave you, I think I answered correctly.
*October 30, 2014*

**Social Studies**

Oh, your answer to the Saratoga question is correct for sure.
*October 30, 2014*

**Social Studies**

I think c was true. I do not think more than half the colonists were Loyalists.
*October 30, 2014*

**math**

7 have black or brown total = 4+3+1+2 = 10 7/10 You can multiply top and bottom by 6 if you want, but no different :)
*October 30, 2014*

**Calculus**

3 * (x^10 - 1)^2 * 10 x^9 or 30 x^9 (x*10 - 1)^2
*October 30, 2014*

**Algebra 2**

20 x - 1 y = -200 25 x - 1 y = 0 D = -20 + 25 = 5 Dx = | -200 -1 | | +000 -1 | / 5 = 200/5 = 40 sign ? Dy = | 20 -200 | | 25 +000 | /5 = 5000/5 = 1000
*October 29, 2014*

**Please help-algebra**

yes
*October 29, 2014*

**Please help-algebra**

Jacqueline, please read the problem again.
*October 29, 2014*

**Please help-algebra**

no .15*number + 10 0.15 x + 10
*October 29, 2014*

**Please help-algebra**

Which do you think? 15 cents times the square feet plus a 10.00 trip fee
*October 29, 2014*

**MATH FOR THE OFFICE**

31 2/8 - 29 3/8 = 30 10/8 - 29 3/8 = 1 7/8
*October 29, 2014*

**Math Help Please! ASAP!**

no y + 5 >7 subtract 5 from both sides y > 2 The second one is right
*October 29, 2014*

**Algebra: Answer Check**

No, I do not think so, suspect typo in numerator. It should be possible to factor.
*October 29, 2014*

**Algebra: Answer Check**

-3*16 -8*5 + 2 +7 -48 -40 + 9 -88 + 9 -79
*October 29, 2014*

**Physics**

momentum east = 20*3 = 60 momentum north = 30 * 2 = 60 momentum east = 50*Ve = 60 momentum north = 50*Vn = 60 Ve = 6/5 Vn = 6/5 angle = 45 speed = (6/5) sqrt 2
*October 29, 2014*

**physics**

see the problem just above this one
*October 29, 2014*

**Physics**

F = m g sin 34 = 120 x x = (1/120)(3)(9.8) sin 34
*October 29, 2014*

**Calculus**

a) 973 + .0685 ( 81000 - 20000) b) T = .9 x c) L = 973 + .0685 (.9 x - 20000) d) 973 + .0685 (.9*90000 - 20000) same as a above
*October 29, 2014*

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