Friday
October 31, 2014

Posts by Damon


Total # Posts: 19,077

geometry
1 m / 2 cm 14 cm (1 m / 2 cm) = 7 m 20 (1/2) = 10 m 7 (1/2) = 3.5 m
August 12, 2014

Math
14 = 7*2 always :) (x-7)(x+2) ------------------ b(Ab+3) ----------------- suspect you mean a^3-8a^2+15a which is a (a^2-8a+15) but we know 15 = 3 * 5 and 3+5=8 :) so a (a-5)(a-3)
August 12, 2014

math
circles are all geometrically similar to each other so all lengths scale the same. Both the diameter and the circumference are lengths. (1/2) 8 = 4
August 12, 2014

arithematic
1000 = (v+c)15 = 15 v + 15 c 1000 = (v-c)30 = 30 v - 30 c ------------------------------- 2000 = 30 v + 30 c 1000 = 30 v - 30 c ------------------ subtract 1000 = 60 c etc
August 12, 2014

Algebra
5 + 4 (2)^2 = 5 + 4 (4) = 5 + 16 = 21
August 12, 2014

Algebra
(4 * 1/10)^3 = 64 * 1/1000 = .064
August 12, 2014

Algebra
2*2*5 x^5 u^7 and 2*2*7 x^3 v^2 u^4 4 x^3 u^4
August 11, 2014

Analytic Geometry
sketch it first then find the lengths of the sides for example c^2 = 2^2 + 6^2 = 40 c = 2 sqrt 10 then use law of cosines a^2 = b^2 + c^2 - 2 b c cos A
August 11, 2014

Analytic Geometry
intersections: x^2 + y^2 - 2x - 2y -2 = 0 x^2 + y^2 + 2x + 2y -2 = 0 ---------------------------subtract -4x -4y = 0 x = - y so along that line of slope -1 now where does x = -y on either circle? 2 y^2 + 2y -2y = 2 y^2 = 1 y = +/- 1 x = -/+ 1 in other words at (-1,1) and (1,-1...
August 11, 2014

Analytic Geometry
I think you mean "VERTICES" or "corners" in geometry where two straight lines meet.
August 11, 2014

math
5^3 - 2^3
August 11, 2014

math
so this time they add to 90
August 11, 2014

math
supplementary angles add to 180 93 + x = 180 or x = 180 - 93
August 11, 2014

physics
250 (1000/3600) = 69.4 m/s v = Vi + a t 0 = 69.4 -10t t = 6.94 seconds to stop d = (1/2) a t^2 = (1/2)(10)(6.94^2) = 241 meters
August 11, 2014

statistics gibberish
Please proof read does body mean boys? what is 60 kg ? who got hired for what? http://davidmlane.com/hyperstat/z_table.html
August 11, 2014

Algebra
2 v^2 + 4 v - 14 = v^2 + 2 v + 1 v^2 + 2 v - 15 = 0 (v+5)(v-3) = 0 v = 3 or -5 the next one is easy
August 11, 2014

Algebra
L = 7 + 2 w L w = 99 (7+2w)w = 99 2 w^2 + 7 w - 99 = 0 (2w -11)(w+9) = 0 w = 11/2 L = 7 + 11 = 18
August 11, 2014

chemistry
By the way molecules of He is the same as atoms of He because there is one atom per molecule. If it had been H2 or O2 there would have been twice as many mols of atoms as mols of molecules.
August 11, 2014

chemistry
3 times Avagadro's number = 3 * 6.022 * 10^23 = lots of them Hey saying you have a mol of something is the same as saying you have 6*10^23 of them. It is sort of like if you say you have a dozen everyone knows you have twelve.
August 11, 2014

Calculus-Math
dC/dt = dC/dx dx/dt = 60 dx/dt = 60 [ 3(-1.637) t^2 etc
August 11, 2014

Algebra
2*3*5* w^4 * v^8 and 2*2*2*3 * y^3 * w^6 *v^2 2*3* w^4 *v^2 or 6 w^4 v^2 is all that is common
August 11, 2014

Algebra
I just did this about one minute ago. Stop spamming.
August 11, 2014

Geometry
NO lots of things with 4 straight sides are not rectangles but squares are.
August 11, 2014

Algebra
You are welcome.
August 11, 2014

Algebra
w (9-w^2) second factor is difference of squares in general a^2-b^2 = (a-b)(a+b) so w (3-w)(3+w) or -w (w-3)(w+3)
August 11, 2014

physics
Ah, ha, there was more. initial south momentum = 900 v initial west momentum = 2000 u final south momentum = 2900(16)cos 24 final west momentum = 2900(16)sin 24 so 900 v = 46400 (.9135) and 2000 u = 46400 (.4067)
August 11, 2014

algerbra
draw a number line from way left to way right +54 - (-17) = 54+17
August 11, 2014

Maths literacy
base times height. It is the same as a rectangle with a triangle taken off one end and tacked to the other end. Draw it.
August 11, 2014

Maths literacy
of what ? circle pi r^2 square s^2 rectangle L w general integral of dy dx ?
August 11, 2014

math
1= integral f(x) dx from 0 to 1 over 1 1= .5 a x^2 + (1/3) b x^3 from 0 to 1 1= .5 a + b/3 and .6 = E(x) = integral x f(x) dx .6 = = integral a x^2 + b x^3 .6 = (1/3) a + (1/4) b solve those two equations for a and b then you can do f(x) from 0 to 1/2 etc
August 11, 2014

Math
http://davidmlane.com/hyperstat/z_table.html
August 11, 2014

physical science
Just did, scroll down one question
August 11, 2014

physics
H2O = 2 + 16 = 18 grams / mol 30/18 = 1.67 mol 1.67 * Avagadro's number 1.67 * 6.022 * 10^23 = 1.004 *10^24 molecules which is quite a few
August 11, 2014

Physics
I have done several, your turn.
August 11, 2014

PHYSICS
yes * means "times"
August 11, 2014

PHYSICS
a = (.90 -0)/2.8 weight = m g = 50 (9.81) friction force = .2 * 50 (9.81) F - .2*50(9.81) = 50 (.9)/2.8
August 11, 2014

physics - so what ?
What is the question?
August 11, 2014

physics
50 min = .833 hr t1 = 3/(1.6+v) t2 = 3/(1.6-v) .833 hr = t1 + t2
August 10, 2014

physics
see this one I just did: http://www.jiskha.com/display.cgi?id=1407726270
August 10, 2014

AP Stats
By the way the formula used for linear regression is at the bottom of that web page if you need it or are doing the regression by hand. Most scientific hand calculators have an app for linear regression.
August 10, 2014

AP Stats
I have no idea what you are talking about unless you mean use regression analysis to find a best linear fit to the data. If that is what you are trying to do, Google linear regression for example there is an online calculator here: http://www.alcula.com/calculators/statistics/...
August 10, 2014

maths
B = J + 2 G = 2 B D = 2 G ---------------- so J = B - 2 G = 2 B D = 2 G = 4 B ------------------ then J + B + G + D = 38 ( B-2 ) + B + 2 B + 4 B = 38 8 B = 40 B = 5
August 10, 2014

physics
v = Vi + a t 20 = Vi + 9.5 a d = Vi t + (1/2) a t^2 108 = (20-9.5 a) (9.5) + (1/2) a (9.5)^2 solve for a
August 10, 2014

Alegbra
I do not know present value formula, using head 125/365 = .34247 so t = 8.34247 A = p e^rt 225,500 = p e^.0855 (8.34247) ln 225,500 = ln p + .71328 ln p = 11.6128 p = $110,502.72
August 10, 2014

Math
c + a = 20 so c = 20-a 12 c + 18 a = 246 12(20-a) + 18 a = 246 240 -12 a + 18 a = 246 etc
August 10, 2014

Physics
YOU MEAN: xf = xo + vot + (1/2)a t^2 How long does it take the first chestnut to reach the ground? 11 = (1/2) g t^2 t = sqrt (22/9.81) = 1.5 seconds so how long is the second one in the air? t = 1.5 - sqrt(2*2.7/9.81) = 1.5 - .74 = .76 seconds so the second one has to go 11 ...
August 10, 2014

math
do they have to be different? If not (1 + 1 + 1 + 45)/4 = 12 if they do have to be different (1 + 2 + 3 + 42)/4 = 12
August 10, 2014

math
Nancy and Sue make 11 bags the first hour all together they make 23 bags per hour they have 149 - 11 = 138 bags to make 138/23 = 6 hours so total of 7 hours 7 * 60 = 420 minutes
August 10, 2014

math typo or nonsens
Huh, Nancy and Sue make 11 bags per hour, not 12 anyway if they working together make 24 bags/hr then 149 bags / 24 bags/hr = 6.2 hr 6.2 * 60 = 372 minutes
August 10, 2014

Algebra
(15x+1)(x+2) is correct to check using FOIL First 15 x^2 Outer 30 x Inner 1 x Last 1 * 2 = 2 so 15 x^2 + 31 x + 2 to check using distributive property of multiplication 15 x ( x+2) = 15 x^2 + 30 x +1 (x+2) = x + 2 sum = 15 x^2 + 31 x + 2
August 10, 2014

Algebra
you turned the sign around in the second line w (9-w^2) w (3-w)(3+w)
August 10, 2014

physics incomplete
the answer to what you have typed is easy if they were both moving 24 deg west of south at 16 before the collision, they can continue after. However I am sure that is not the case and you have left out some initial conditions.
August 10, 2014

physics
loss of potential energy = m g (31) = 62 * 9.81 * 31 = 18,855 Joules gain in potential energy of spring = (1/2) k x^2 =.5 * k (31-12)^2 = 180.5 k so k = 18855/180.5 = 104 N/m F = m a force down = m g = 62*9.81 = 608 Newtons force up = kx when x = 31-12 = 19 F up maximum = 104*...
August 10, 2014

physics
hit at height x ball A drops h-x ball b rises x Ball A (h-x) = h - 4.9 t^2 or x = 4.9 t^2 v = -9.81 t Ball B h = Vi t - 4.9 t^2 v = 9.81 t/2 = 4.9 t so 4.9 t = Vi - 9.81 t or Vi = 14.7 t ------------------ h = 14.7 t^2 - 4.9 t^2 = 9.8 t^2 but x = 4.9 t^2 so I get half way up, ...
August 10, 2014

Algebra
we know that 81 = 9*9 and that 9+9 = 18 so try (u+9)(u+9)
August 9, 2014

Calculus-Math
d/dx (x^2y^2 - 2 x) = 2 x y^2 - 2 d/dx (2 x y^2 - 2) = 2 y^2
August 9, 2014

physics
draw picture get angles in first triangle 180 - 52 = 128 180 -128 - 33 = 19 which is angle opposite the 300 then law of sines sin 19/300 = sin 33/second slope up so second slope = 300 (sin 33 / sin 19) = 502 meters then right triangle sin 52 = h/502 h = 395 meters four ...
August 9, 2014

Calculus-Math
6 (x^2+y^2)(2x+2ydy/dx)=100(2x-2ydy/dx) find dy/dx at (4,-2) 6(16+4)(8-4dy/dx)=100(8+4dy/dx) solve for dy/dx which is m in y = m x + b then use the given point in the given equation to find b
August 9, 2014

Algebra
y^3/y^5 = y^-2 x^6 / x^4 = x^2 so y^-2 x^2 or x^2/y^2 or (x/y)2
August 9, 2014

Precal
r = sqrt (74) theta = tan^-1 (5/7) leave it that way, do not go to degrees 2 r = 2 sqrt(74) draw this axis system to figure out tan theta+pi/2 we are in Quadrant 2 theta degrees from the y axis so now tan of new theta = 7/-5 and we have the point ( 2 sqrt 74 , tan^-1 (-7/5) ...
August 9, 2014

Precalculus
and no it is the whole ellipse
August 9, 2014

Precalculus
.... and how did you make out with the spherical coordinates problem Aditya?
August 9, 2014

physics
First crossing: time to cross = 87/1.5 = 58 seconds so speed of current = 30/58 = .517 m/s second crossing v upstream = 1.5 sin A = .517 sin A = .345 A = 20.2 degrees then if they ask: v across = 1.5 cos A
August 9, 2014

physics
Yes, I am getting a bit frayed around the edges as well.
August 9, 2014

physics
(c) v = sqrt (2 g h)
August 9, 2014

physics
Thrust phase: v = a t v = 17 t v at 20 s = 17 * 20 = 340 m/s (Vi for next phase) h = (1/2) a t^2 = (1/2)(17)(400) = 3,400 m coast up phase: v = Vi - a t v = 0 at top 0 = 340 - 9.81 t t = 34.7 seconds coasting up now 54.7 seconds aloft how high? h = 3,400 + Vi t - 4.9 t^2 h = 3...
August 9, 2014

physics
It takes her 87/1.5 seconds to cross the current flows 30 meters in 87/1.5 seconds so the current speed is 30 *1.5 /87
August 9, 2014

physics
This does not make sense. The only thing I can say is that it has a mass of m = 5.10/9.81 = .52 kilograms wherever it is. Is the spaceship in a "zero gravity" orbit around earth? In that case it still has a gravitational force depending on how far from the center of ...
August 9, 2014

physics
speed across = 7.4 cos 24.8 time = distance/speed = 26.1 / 7.4 cos 24.8 the river speed only says how far downstream he will end up.
August 9, 2014

physics
moved along three sides of square? say 25 m east, 25/15 s then 25 m north, 25/15 s then 25 m west, 25/15 s so displacement is 25 m north in 75/15 s 25 * 15/75 = 15/3 = 5 m/s north
August 9, 2014

Math
If Efram is 63 that is 63 - 52 = 11 years later then Cole is 11 + 25 = 36 so it is indeed in 11 years but 11 not 63, is the answer
August 8, 2014

Math
sure but put it as a new question because we do not always look back
August 8, 2014

Math
x in the pocket to start then 4 + 2 x then 2 (4 + 2 x ) = 100 8 + 4 x = 100 4 x = 92 x = 23
August 8, 2014

MATH
multiply both sides by 12 (the least common multiple of 3 and 4) . 9 x = 2 x = 2/.9 = 20/9
August 8, 2014

algebra
but if you insist on estimating call it 35 / 3 :) which is about 12
August 8, 2014

algebra
it is so fast to say 7 1/5 is 36/5 that I call estimating here going kind of out of my way :)
August 8, 2014

algebra
36/5 / 3/5 = 36/3 = 12
August 8, 2014

Algebra
2.5 * 60 = 150 minutes 30 + .05*150 = 30 + 7.5 = $ 37.50
August 8, 2014

algebra
lol just did 36/5 / 3/5 = 12
August 8, 2014

By the way
Other than that - Good job !
August 8, 2014

Precalculus
http://mathworld.wolfram.com/SphericalCoordinates.html
August 8, 2014

Precalculus
are you sure z is not r cos phi in math theta is usually i the xy plane x = r sin phi cos theta y = r sin phi sin theta z = r cos phi In engineering and physics these conventions are often different, nut I suspect you should be using phi as the angle down from the z axis, not ...
August 8, 2014

math
9 x were boys 8 x were girls 17 x total originally 4 x girls left so then there were 9 x boys 4 x girls 13 x total 9 x - 15 = 4 x 5 x = 15 x = 3 I guess you can do 17 x and 4 x
August 8, 2014

Algebra
I started with Calculus first as well, but changed my mind after drawing the picture.
August 8, 2014

Algebra
angle from x axis to tangent = 45 + sin^-1 ( sqrt 6/3sqrt2) = 45 + 35.3 = 80.26 deg x = 2 sqrt 3 * cos 80.26 y = 2 sqrt 3 * sin 80.26 y/x = tan 80.26 = 5.82
August 8, 2014

Algebra
whoops, sorry h^2 = 18 - 6 = 12 h = 2 sqrt 3
August 8, 2014

Algebra
draw circle, center at (3,3) radius sqrt 6 draw line (hypotenuse it turns out) from (0,0) to (3,3), length is 3 sqrt 2 draw our tangent, hits circle at 90 degree angle to radius to that point, length is h so h^2 = 18 + 6 = 24 h = 2 sqrt 6 I think you can figure out the ...
August 8, 2014

Algebra
where does the tangent to the circle from the origin hit the circle?
August 8, 2014

Ethics
The first one is just accusatory, which just elicits a defensive response. The second one requires that the wrong doers be religious. We can not count on that. Who knows where intuition will lead? So I suppose I will have to agree with you.
August 8, 2014

math
aaarrrggghhhh, feet and inches and stuff :( anyway if g = -32 ft/s^2 then I will have to admit that the distance fallen from a still start is s = 16 t^2 (not r^2 by the way, falls straight down, not in a circle) s = 16 (64) = 1024 answer B which we did not need a calculator ...
August 8, 2014

math
well, if one were a prime number then 1986 would do BUT since it is not (any number greater than one not divisible by anything but ---), then 1987 would do since surely 2 is a prime number.
August 8, 2014

maths
x^2 = (c-b)/a ? x = sqrt [(c-b)/a] well, (c-b)/a better be positive and a square of some integer (which makes it positive anyway) for example if (c-b)/a = 5 then x = sqrt 5 which is hard to express as a ratio of integers and if (c-b)/a is -4 then we have 2 i and i, the square ...
August 8, 2014

Math (fibonacci
It would help if that last date were odd :)
August 8, 2014

Math (fibonacci
By the way I suspect you mean 2000 not 200
August 8, 2014

Math (fibonacci
y = 1985 + x 200 = x + y so 200 = x + (1985+x) back to you :)
August 8, 2014

Physics
yes, good to remember v = -sqrt (2 g h) here v = -sqrt (2*9.81*.75) = -3.84 m/s 1.7 = sqrt (2 *9.81 * h) h = .1472986748 I think g is 9.81, you use 9.8 some classes use 10
August 8, 2014

science
I think I know what you mean. If you calculated the time until the ball reached maximum height and called that time t, then the total time in the air is 2t by symmetry
August 8, 2014

science
yes they both start with Vi = 0 and accelerate downward at 9.81 m/s^2
August 8, 2014

Physics
You are welcome.
August 8, 2014

Physics
yes, 0 = 42 + 75 a a = - .56 d = Vi t + .5 a t^2 d = 42(75) - .28(75)^2 = 3150 - 1575 = 1575
August 8, 2014

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