Thursday

May 5, 2016
Total # Posts: 40,202

**math plz its urgent**

I also think B is correct. Starts at -4 and keeps going down by 2 each step.
*March 16, 2016*

**Statistic**

play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html and you can see how it works.
*March 16, 2016*

**geometry**

thank you
*March 16, 2016*

**geometry**

I agree.
*March 16, 2016*

**geometry**

Find the missing value to the nearest hundredth. tan ___ = 73 a- 81.61 b- 64.61 c- 60.61 d- 89.22 My answer is D
*March 16, 2016*

**math**

volume of earth is π*(3/2)^2 * 14 = 63π/2 m^3 The area of the ring is π(4 + 3/2)^2 - (3/2)^2) = 28π m^2 So, the thickness of the ring is (63π/2 m^3) ÷ (28π m^2) = 9/8 m
*March 16, 2016*

**Math**

just be counting things when she's around. (No, not all the time, just when it seems like an opportune moment.) When she's ready, she'll take an interest, and then watch out; there'll be no stopping her. I don't know how many sheets of paper I used up as a ...
*March 16, 2016*

**Math**

subtract 2 1/2 from both sides. That gives you b = 3 1/4 - 2 1/2 now simplify: b = 3/4
*March 16, 2016*

**Math/Precal**

sinx/(1-cosx) = sinx(1+cosx) / (1-cosx)(1+cosx) = sinx(1+cosx) / (1-cos^2x) = sinx(1+cosx) / sin^2x = (1+cosx)/sinx
*March 16, 2016*

**maths**

If the perimeters differ by 32, the sides differ by 8. s^2 + (s+8)^2 = 610 Now just find s and s+8.
*March 16, 2016*

**maths**

Of course, 1+2+3 does equal 1*2*3
*March 16, 2016*

**Math/precal**

not a joke. Just checking your knowledge of common identities and angles. So, the exact value is 0/1 = 0.
*March 16, 2016*

**GEOMETRY/ALGEBRA**

So, only B appears correct. C would work, if you consider 0.1 min/cm^3 a rate. Usually rates are written with time in the denominator. If, however, you want to determine the time needed to fill 1 cm^3, then C will work.
*March 16, 2016*

**math**

If the domain is {-3,0,1,5} then A
*March 16, 2016*

**maths**

You have some matching problems with braces and parens, but 2(fg)(2) = 2*f(2)*g(2) = 2*3*2 = 12 (f/g-2f)(3) = f(3)/g(3) - 2f(3) = 6/1 - 2*6 = -6 (f-g)(4) = f(4)-g(4) = 9-2/3 = 8 1/3 kobe needs to step back and take a breath.
*March 16, 2016*

**calculus help!!!!! plz**

As written, you have ∫cosx + 2/cosx + sinx dx which is just trivial: sinx + 2ln(secx+tanx) - cosx + C So, I'll assume you meant ∫(cosx + 2)/(cosx + sinx) dx That's tougher than it looks. cosx/(cosx+sinx) = 2cosx/2(cosx+sinx) = (cosx+sinx + cosx-sinx)/2(cosx...
*March 16, 2016*

**Maths\relation&function**

the domain of f+g is D(f) ∩ D(g) = {1,2} For other values, both f and g are not defined, so f+g cannot be defined. f+g = {(1,2+5),(2,5+5)} = {(1,7),(2,10)} do f-g the same way.
*March 16, 2016*

**sequence help!!!!! plz steve,reiny,damon,bob...anyone!!!!**

I suspect a typo. 6 = 1^3+5 13 = 2^3+5 32 = 3^3+5 69 = 4^3+5 130 = 5^3+5 221 = 6^3+5 If no typos, then I'm stuck, too.
*March 16, 2016*

**Calculus**

I'm intrigued how you got all those odd values for the areas when the width of each rectangle is 2 ....
*March 15, 2016*

**Calculus**

draw a diagram. At time t hours, the distance z is z^2 = (20t)^2 + (25t)^2 now just figure dz/dt at t=2.
*March 15, 2016*

**Math**

well, the sides are 4, 4√3 and 8
*March 15, 2016*

**math**

such a reflection moves (x,y) -> (-x,y)
*March 15, 2016*

**Math**

beats me. I don't see any variables at all. usually the independent values are listed first.
*March 15, 2016*

**math**

use a common denominator of 21
*March 15, 2016*

**Algebra**

x+y=38 y=x+8
*March 15, 2016*

**math**

h/50 = sin54°
*March 15, 2016*

**Math**

correct
*March 15, 2016*

**math**

If the tank is on end, then if the depth is d ft, the volume is π*3^2*d = 9πd ft^3 So, if 2 ft deep, that's 18π=56.5 ft^3 However, if the tank is lying on its side, so the axis is horizontal, then we have to figure the area of a circular segment - the cross-...
*March 15, 2016*

**Math**

correct, but the ratio also increases. The volume grows faster than the area. Consider a cube of side s. v = s^3 a = 6s^2 v/a = s/6 So, the actual ratio depends on the size of the cube. No matter what the shape, the ratio of volume to area gets larger and larger as the size ...
*March 15, 2016*

**Math**

the triangle has three equal sides, then it is equilateral, so each of its angles is 60° The square's angles are all 90°. So, starting at the bottom of the triangle, and moving around, the angles are 60, 60+90=150, 90, 90, 150 Note that as with any pentagon, the ...
*March 15, 2016*

**Geometry**

No explanation needed, if you recall that the sum of the interior angles of a polygon with s sides is 180(s-2). So, 180(s-2) = 2880
*March 15, 2016*

**math**

The nth term is n. The sum of n terms is n(n+1)/2
*March 15, 2016*

**Trig identity.**

sin4x = 4sinxcos - 8sin^3x cosx sin4x = 4sinx*cosx(1-2sin^2x) sin4x = 4sinx*cosx(cos2x) sin4x = 2(2sinx*cosx)(cos2x) sin4x = 2(sin2x)(cos2x) sin4x = sin(2*2x) sin4x = sin4x cos3x cos(x+2x) cosx*cos2x - sinx*sin2x cosx(1-2sin^2x) - sinx(2sinx*cosx) cosx(1 - 2sin^2x - 2sin^2x) ...
*March 15, 2016*

**Trig help**

#1 must be a joke. sin2x=sin2x for all x #2 tan2x + tanx = 0 2tanx/(1-tan^2(x)) + tanx = 0 2tanx + tanx(1-tan^2(x)) = 0 tanx (2 + 1-tan^2x) = 0 tanx=0 tanx = ±√3 so, x=kπ or kπ ± π/3 Now just use the values of k so that the results come out ...
*March 15, 2016*

**math**

3 1/4 * 10 = 30 10/4 = 32 1/2
*March 15, 2016*

**math -oops**

My bad. opens to the left: x = ay^2 -1 = a*2^2 a = -1/4 x = -1/4 y^2 or y^2 = -4x http://www.wolframalpha.com/input/?i=y^2+%3D+-4x
*March 15, 2016*

**math**

vertex at (0,0) means y = ax^2 So, plug in (-1,2) and you have 2 = a(-1)^2 a = 2 so, y = 2x^2
*March 15, 2016*

**Calculus**

Hmmm. Let's trudge through those words. We have ∫[2,8] g(x) dx = 5 ∫[6,8] g(x) dx = -3 we know that ∫[2,6] + ∫[6,8] = ∫[2,8] ∫[2,6] + (-3) = 5 ∫[2,6] g(x) = 8 ∫[2,6] 2g(x) = 2*8 = 16 Forgot that 2, eh?
*March 15, 2016*

**Calculus**

Nope. ∫ 1/(x^2+1) dx :: not so simple here. You need x = tanθ The 2nd is the same, unless there are some groupings you have omitted. ∫ x/(x^2+1) dx :: u = x^2+1 ∫ x^3/(x^4+1) dx :: u = x^4+1
*March 15, 2016*

**Calculus**

nope. sums and differences work that way, but not products. Consider f(x) = x g(x) = x ∫f * ∫g = 1/2 x^2 * 1/2 x^2 = 1/4 x^4 ∫fg = ∫x^2 = 1/3 x^3 ∫f-g = ∫f - ∫g TRUE ∫[a,a] f(x) dx = 0 NOT 2∫[0,a] ∫3+f = ∫3 + &#...
*March 15, 2016*

**Calculus**

∫[0,2] e^(4x) dx = 1/4 e^(4x) + C [0,2] = (1/4 e^8 + C)-(1/4 e^0 + C) = 1/4 (e^8 - 1) remember that e^0=1, not 0.
*March 15, 2016*

**Calculus**

I assume that ‡ means ∞ You know that ln(x) is only defined for x in (0,∞) Your answer holds for f(x) = ln(|x|), not ln(x)
*March 15, 2016*

**Calc**

∫[2,5] 2+√x dx Looks like the last one to me. The three intervals are [2,3],[3,4],[4,5] The right endpoints are at 3,4,5, NOT 0,1,2,3
*March 15, 2016*

**Geometry**

true
*March 15, 2016*

**maths**

the lengths are in the ratio √(25/9) = 5/3
*March 15, 2016*

**Calculus**

x^2 y + ax - 2/5 (10+2a) y = 0 2xy + x^2y' + a - 2/5 (10+2a)y' = 0 y'(x^2-2/5 (10+2a)) = -(2xy+a) y' = 5(a+2xy)/(4(a+5)-5x^2) y" = 5(2y + 2xy')(4(a+5)-5x^2) - 5(a+2xy)(-10x) ----------------------------- (4(a+5)-5x^2)^2 5(2y + 2x(5(a+2xy)/(4(a+5)-5x^2...
*March 15, 2016*

**Calculus**

first off, if (2,2.5) is an inflection point, then it is on the graph. That means x^2 y + ax + by = 0 4*2.5 + 2a + 2.5b = 0 10 + 2a + 2.5b = 0 5/2 b = -(10+2a) b = -2/5 (10+2a) That gives us x^2 y + ax - 2/5 (10+2a) y = 0 y = -ax/(x^2 - 2/5 (10+2a)) = 5ax/(4(a+5)-5x^2) y'...
*March 15, 2016*

**Pre-Calc**

If it passes through (-2,16) and (-2,0) and (-32,0) then by symmetry the center must be at (-17,8) Now we can use any of the points to find that r = 17 so (x+17)^2 + (y-8)^2 = 17^2 see http://www.wolframalpha.com/input/?i=plot+%28x%2B17%29^2+%2B+%28y-8%29^2+%3D+17^2,+x%3D-2,y%...
*March 15, 2016*

**precalc**

well, geez, just factor out the e^(-2x): e^(-2x) (5x^2-3x^3) = 0 e^(-2x) x^2 (5-3x) = 0 That help?
*March 15, 2016*

**precalc**

2^(-x) (2^(2x) + 2*2^x - 8) = 0 2^(-x) is never zero, so that means you must have 2^(2x) + 2*2^x - 8 = 0 (2^x+4)(2^x-2) 2^x is never negative, so that means 2^x-2=0 2^x=2 x=1
*March 15, 2016*

**Algebra 2**

I'd say just solve for n. But looking here http://www.wolframalpha.com/input/?i=n^2%3D%281%2F2n%2B10%29%281%2F2n-2%29 it appears there is no solution. A typo in the problem?
*March 15, 2016*

**Math**

y = 6(1.21)^t 1.21 = e^ln(1.21) = e^0.19 y = 6*(e^0.19)^t = 6*e^(0.19t) Now you can work the rest
*March 15, 2016*

**Calculus**

you might start by reading up on Euler's method. google can help. There's even a youtube video illustrating the method. There's a good discussion with examples here: http://tutorial.math.lamar.edu/Classes/DE/EulersMethod.aspx
*March 15, 2016*

**math**

use 1/4 of 3c water and 1c cereal So, that's 1/4 c cereal.
*March 14, 2016*

**Math**

.75x = 30 x = 40 or, using fractions, 3/4 x = 30 3x = 120 x = 40
*March 14, 2016*

**Pre-Calc**

Grrrr! pi, not pie!!! Pie is what you eat. Other than that, why not use real math symbols, instead of all those messy words?? tan θ = -√22/11 and π/2 < π < π Draw the triangle in standard position. tanθ = y/x = √22/-11 sinθ = y/r...
*March 14, 2016*

**calculus**

see related questions below. And http://math.stackexchange.com/questions/225718/find-the-volume-of-the-largest-right-circular-cone-that-can-be-inscribed-in-a-sp
*March 14, 2016*

**calculus**

it is clear that h = 2r, so v = 1/3 πr^2 h = π/12 h^3 dv/dt = π/12 h^2 dh/dt so, now just crank it out: π/12 * 8^2 dh/dt = 8 dh/dt = 3/(2π) m/min
*March 14, 2016*

**calc**

xy=50, so y=50/x a = (x+4)(y+8) = (x+4)(50/x + 8) a = 8x + 200/x + 82 da/dx = 8 - 200/x^2 da/dx=0 if x=5 so, the inside dimensions are 5x10 and the outside is 9x18
*March 14, 2016*

**calculus**

a = 4πr^2 at t=2, a=52, so r=√(13/π) da/dt = 8πr dr/dt so, you need 8π√(13/π) dr/dt = 26 dr/dt = 1/4 √(13/π)
*March 14, 2016*

**Math (geometry)**

the whole circumference is 7926π. half the way around is 3963π. since the plane goes 550 miles each hour, it will take 3963π/550 = 22.6 hours
*March 14, 2016*

**Geometry**

You are correct. Draw a diagram, and if the belt's length is x, then 12/x = sin60°
*March 14, 2016*

**math**

35 * 6/7 * 4/5 = 24
*March 14, 2016*

**Algebra**

Your answer is right, but you should have typed the problem correctly.
*March 14, 2016*

**Algebra**

since every term has a "c" in it, 2c is the GCF, not just 2.
*March 14, 2016*

**math**

I'll write it, and then it'll be right. (2.74+5.6)x10^7 = 8.34x10^7
*March 14, 2016*

**Alegbra**

all multiples of 3-4-5 5-12-13 7-24-25 and other common sizes. I expect you can google the topic of pythagorean triples and find a suitable list.
*March 14, 2016*

**Trigonometric Identities**

tan(A+B) = (tanA+tanB)/(1-tanAtanB) that should get you started.
*March 14, 2016*

**Trigonometric Identities**

tanA-sinA = sin(1/cos - 1) see where that takes you.
*March 14, 2016*

**math**

I don't have the choices, but I suspect (0,4) was one of them. Then you'd have a 3-4-5 right triangle. If that's not one of them, then you'll have to check dot products. If one of the dot products is zero, then those two vectors are orthogonal.
*March 14, 2016*

**Happy Pi Day, 2016**

I find it transcendental.
*March 14, 2016*

**Calculus**

after the integration, you have arctan(1) - arctan(a) = arctan(1/a) - arctan(1) π/4 - arctan(a) = arctan(1/a) - π/4 rearrange the terms and you're done.
*March 14, 2016*

**Math**

area of triangle times the length.
*March 14, 2016*

**Math**

holy crap! Ever hear of math sumbols? 3/7, 2/3, 2/5 Change them all to a common denominator of 105
*March 14, 2016*

**Geometry**

20 = 4*5 15 = 3*5 LCM(15,20) = 3*4*5 = 60 every 60 seconds one train does 3 laps, and other does 4 laps.
*March 14, 2016*

**solomon mahlangu high**

math, computer science, music Now, what are your preferences?
*March 14, 2016*

**maths -quadratic eqn**

read up on the discriminant of a quadratic: b^2-4ac
*March 14, 2016*

**Maths**

its, not it's in this context. a+17d = 25 since d=2, it is simple to get a. Then, since 49-25=24, and 24/2 = 12, the 18+12=30th term is 49.
*March 14, 2016*

**Maths**

huh????? nearest meter means an integer value. What's the integer closest to 9.9?
*March 14, 2016*

**maths**

http://www.jiskha.com/display.cgi?id=1457884163
*March 14, 2016*

**Algebra**

You just write down what they told you. width: w length: 2w-3 Then you try to remember the way perimeter is calculated. 2(w + 2w-3) = 48 Then you solve for w, and use that to get the length.
*March 13, 2016*

**science**

PV = kT. So, PV/T is constant. In fact, since T is constant as well, PV is constant. You want P so that 17.5P = 3*3.5
*March 13, 2016*

**science**

given a constant level of energy use, every bit generated from geothermal sources will mean that a similar amount less will be used from fossil fuels. Of course, the relationship is not quite so simple, but that's the general idea.
*March 13, 2016*

**Science**

change in speed over time. So, (70-15)m/s / 10min = 4.5 m/s/min Most people feel more comfortable with just two units, so that would be 4.5/m/s/min * 1min/60s = 4.5/60 = 0.075 m/s^2
*March 13, 2016*

**science computer**

max = 0 maxname = "" for i=1 to 10 read name,age if age > max then max=age maxname=name end if next i print "The oldest person is ",maxname
*March 13, 2016*

**algebra**

enter your coefficients at the URL below and see all the details. http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
*March 13, 2016*

**Math**

since the balls are replaced, the draws are independent events. Just multiply all the probabilities: 5/10 * 3/10 * ...
*March 13, 2016*

**Math**

If A's speed is a, then B's speed is a+1 since time = distance/speed, 480/(a+1) = 480/a - 40 a = 3 m/s
*March 13, 2016*

**math**

P(t) = -3400 + (4900-(-3400))/4 t = -3400 + 83.25t
*March 13, 2016*

**math**

draw a diagram. Review the cotangent function. Then you will see that if the cliff has height h feet, h cot42° - h cot54° = 15
*March 13, 2016*

**Algebra**

well, you have 7x = 3y y = 7/3 x 7/3 is the constant of variation. when one says y varies directly with x, it means that there is a constant k such that y = kx If y varies inversely as x, then there is k such that xy = k or, y = k/x These can be combined, so that if you hear y...
*March 13, 2016*

**science**

well, since no mass is lost, ...
*March 13, 2016*

**Algebra**

y = 1/4 x
*March 13, 2016*

**math**

2/5 x - (5/7)(2/5 x) + 62 = x x = 70
*March 13, 2016*

**Trig**

AD/sin75° = 100/sin65° AD = 106.58 CD^2 = 50^2 + 106.58^2 - 2*50*106.58 cos50° CD = 83.72 Hmmm. we're close. Better check (a) my math (b) your math On part b, ya got me. what are α and β supposed to be? Maybe they are to be substituted for the actual ...
*March 13, 2016*

**Maths**

5a - 5b = 100
*March 13, 2016*

**maths**

fix your typos.
*March 13, 2016*

**Math**

v varies as r^3. 729 = 9^3.
*March 13, 2016*

**maths**

59 = 2+19d Now you can find d. 6th from the end is T15 = 2+14d.
*March 13, 2016*

**math**

a = πr^2 + 2πrh so, plug in r=14 and h=35 and do the math.
*March 13, 2016*