Tuesday

May 3, 2016
Total # Posts: 40,093

**Calculus**

there are many handy Riemann um calculators online, such as http://www.emathhelp.net/calculators/calculus-2/riemann-sum-calculator/
*April 19, 2016*

**Calculus (Urgent, please)**

The curves intersect at (±1.25,1.56) using symmetry, the area is a = 2∫[0,1.25] √(4-x^2) - x^2 dx = 3.35
*April 19, 2016*

**Math**

7/10 + 7/20 = 21/20 So, 1/20 prefer both. But how can someone prefer two days?
*April 19, 2016*

**math**

your files are not available to us online.
*April 19, 2016*

**math**

9999 * 100
*April 19, 2016*

**Math**

y = x+12 3y-5x = 20
*April 19, 2016*

**Math No!**

nope. He spent that money, and 700 was left. So, x - x/4 - 2x/5 = 700 x = 2000 1/4 of 2000 = 500 2/5 of 2000 = 800 So, he spent 1300, leaving 700
*April 19, 2016*

**Math**

since there is no question, I see little point in hinting at answers.
*April 19, 2016*

**science**

try google
*April 19, 2016*

**maths**

not sure what "to s" means, but a suitable trapezoid has only two right angles.
*April 19, 2016*

**math**

last I checked, there were 435 reps. and that's there, not their!
*April 19, 2016*

**Maths**

√(12+6√3) + √(12-6√3) 12+6√3 = 9 + 6√3 + 3 = (3+√3)^2 so, you have just 3+√3 + 3-√3 = 6
*April 19, 2016*

**advanced calculus**

The central arm's endpoints are a circle of radius 100: x = 100cosθ y = 100sinθ At θ=0, the arm is horizontal. So, assuming the wheel's boarding position is also at θ=0, and its angle is relative to the central arm, the boarding location's ...
*April 19, 2016*

**Calculus**

The region is just a square of side √2, with its center at (2,1). Using the Theorem of Pappus, the surface area is thus the perimeter of the square times the distance traveled by its centroid: a = 4√2 * 2π = 8π√2 Doing it using the usual definition...
*April 19, 2016*

**math**

you really need to work on your text formatting.
*April 19, 2016*

**Calculus I**

you can verify this at http://www.wolframalpha.com/input/?i=plot+y%3D1%2F12+x^3,+y%3D4x-32%2F3,+0%3C%3Dx%3C%3D6
*April 19, 2016*

**Calculus I**

f(x) is a constant, so the slope is zero everywhere!!
*April 19, 2016*

**Pre-Calc**

logb(4) sqrt((x^7 y^2)/(z^4)) well, I'm not sure what logb(4) has to do with it, but log(a^n) = n*log(a) so, log(√(x^7y^2/z^4)) = 1/2 (7logx + 2logy - 4logz) = 7/2 logx + logy - 2logz regardless of the base.
*April 18, 2016*

**Math college grade 12**

well, 0.8^t = 1/300 t log0.8 = -log300 ...
*April 18, 2016*

**Math-Trig**

the diagonals bisect each other, and are perpendicular to each other. So, draw the figure, and note the four right triangles formed.
*April 18, 2016*

**geomatry**

(-1-(-5))/(-4-2) = 4/-6 = -2/3
*April 18, 2016*

**math**

you can't. If all you have is the volume, it could be a cube of side ∛10 or, a brick with sides 1 x 2 x 5 2 x 2 x 2.5 4 x 2 x 1.25 10 x 5 x 0.2 etc.
*April 18, 2016*

**Calculus**

(ds)^2 = (dx/dt)^2 + (dy/dt)^2 = (-sint + sint + tcost)^2 + (cost - cost + tsint)^2 = t^2cos^2(t) + t^2sin^2(t) = t^2 so, ds = dt that's pretty easy to integrate, right? Hmmm. I missed that ^2 hanging out there. Is y(t) = sint - t(cost)^2 or y(t) = sint - tcos(t^2)? In ...
*April 18, 2016*

**Solid Mensuration**

google is your friend. You might start here: http://www.contracosta.edu/legacycontent/math/stararea.htm
*April 18, 2016*

**Math**

5n+25q = 460 n+q = 28 now just solve for n and q.
*April 18, 2016*

**Geometry**

looks good to me.
*April 18, 2016*

**Geometry**

at the fold. unless you fold it the other way, and then it would still be the 50-yd line...
*April 18, 2016*

**Math**

If the dimensions are x and y, then if the change fraction was r, xy = 300 (xr)(yr) = 363 xyr^2 = 363 r^2 = 363/300 r = 1.1 so, a 10% increase was used.
*April 18, 2016*

**math**

c+t=30 3c = 2t
*April 18, 2016*

**Math**

h(t) = 1 + vt - 16t^2 max height is reached at t = v/32, so 1 + v(v/32) - 16(v/32)^2 = 35 v = 8√34 h(t) = 1 + 8√34 t - 16t^2 h=0 at t=2.94 v(t) = 8√34 - 32t, so when h=0, v = 8√34 - 32(2.94) = -47.43 ft/s
*April 18, 2016*

**Trigonometry**

well, geez, just solve the equation. r = v^2sin2θ/g 1/32 1200^2sin(2θ) = 3000 sin2θ = (32*3000)/1200^2 = 1/15 Of course, there are two solutions, since sinθ is positive in [0,pi]. But you want the minimum value.
*April 18, 2016*

**Math**

clearly the answer cannot be 1, since that would mean you always get tails or roll less than 4. there are 12 possible outcomes, easy to list them. 1/2 give tails 1/2 * 3/6 = 1/4 gives heads and n<4. 1/2 + 1/4 = 3/4 or, consider P(heads & n>=4) = 1/2 * 1/2 = 1/4 you want ...
*April 18, 2016*

**math**

1.00 = 100% decrease by 17% leaves 83% = 0.83
*April 18, 2016*

**Precalculus**

consider the circle r = 2cosθ that is (x-1)^2+y^2 = 1 clearly r = 2scosθ is just a scaled up version of that. (x - s)^2 + y^2 = s^2 r = 2scos(θ+t) is just a rotated version, turned through angle t. Since t can be anything from 0 to 2pi, the center of our circle ...
*April 18, 2016*

**Math**

(3cm)^3 * 6 = 27*6 cm^3 = 162 cm^3
*April 18, 2016*

**Math**

that will be 1/2 + 1/2 * 1/6 = 1/2 + 1/12 = 7/12 you want P(heads OR (tails and n=3))
*April 18, 2016*

**math**

(x,y) -> (-x,y) so, just change the sign of the x-coordinates.
*April 18, 2016*

**Math**

parallel? I think not. They are the same line. Any solution to one also fits the other.
*April 18, 2016*

**Trig**

or island B
*April 18, 2016*

**Math**

width=w length=2w-5 perimeter: 2(w+l) = 2(w+2w-5) = 2(3w-5) = 6w-15 area: wl = w(2w-5) = 2w^2-10w that wasn't so hard, now, was it?
*April 18, 2016*

**math**

nope. sqrt(256) = 16 A is all irrational. and that's pi, not pie!
*April 18, 2016*

**Trig**

no cosine. the hypotenuse does not come into the calculation.
*April 18, 2016*

**Trig**

you draw a picture fer pete's sake! Then, having reviewed your basic trig functions, you will see that the height h is found from h/60 = cot35°
*April 18, 2016*

**math**

cube: 28^3 pyramid: (1/3)(28^2)(16) now just add 'em up
*April 18, 2016*

**math**

If train B's speed is x, then A's is x-6 Since time = distance/speed, 200/(x-6) = 230/x
*April 18, 2016*

**Calculus**

where did the 0 come from? also you cannot have cos and cos in f'.
*April 18, 2016*

**Calculus**

well, it's easy enough to see whether an answer is right. If f^-1(2) = x, then f(x) = 2 clearly not. It appears you want (f^-1)'(2) f'(x) = 7-3sinx+2cosx f'(2) = -3sin2+2cos2 (f^-1)'(2) = 1/f'(2)
*April 18, 2016*

**calculus**

nasty, until you note that f(x) = (x+1)/(2x+1) f'(x) = -1/(2x+1)^2
*April 18, 2016*

**Math**

see related questions below.
*April 18, 2016*

**Trigonometry Help please**

z^n = r^n cis(nθ)
*April 18, 2016*

**math calculus**

y = x^(2/3)(10-x) = 10x^(2/3) - x^(5/3) y' = (20/3)x^(-1/3) - (5/3)x^(2/3) = 5/3 (4-x)/x^(1/3) y'=0 when x=4 y increases when y'>0, or x<4 see the graph and info at http://www.wolframalpha.com/input/?i=x^%282%2F3%29%2810-x%29
*April 18, 2016*

**Algebra**

well, you need 3x+4 >= 0 at x=-4/3, y=-5, its minimum value.
*April 18, 2016*

**math**

You have seriously garbled the question. It looks like a straightforward law of cosines problem. The distance d is found using d^2 = 12^2+5^2 - 2*12*5 cos37°
*April 18, 2016*

**Math**

the 2nd equation is 0.04176x + 0.01782y = 0.01034 then since you have y, 0.04176x + 0.01782(0.4276-x) = 0.01034 0.02394x = 0.0027202 x = 0.1136
*April 18, 2016*

**Algebra**

make that Range = [-5,∞)
*April 18, 2016*

**Algebra**

I assume you mean y = 2√(3x+4)-5 the domain of √x is x >= 0, so here you must have 3x+4 >= 0 x >= -4/3 That is, the domain is [-4/3,∞) Since √(3x+4)=0 at x=-4/3, the range is [5,∞)
*April 18, 2016*

**math**

9Am, of course. But the watch shows 9:00AM - 0:2*48 = 7:24 AM
*April 18, 2016*

**math p.s. is very hard**

when x changes by 1, y changes by -5. So, the slope is -5 y = -5x + b Since when x=0, y=-1, y = -5x-1
*April 18, 2016*

**Algerbra (Please help ASAP)**

and F as well.
*April 18, 2016*

**algebra**

1/b - 1/a = 1/c - 1/b b-a = (c-4)-b b/a = (c-3)/b I get c=12
*April 18, 2016*

**math- algebra 2**

20000 * 1.05^13
*April 18, 2016*

**Trigonometry**

(3cis27°)^5 = 3^5 cis135° = 243 (1/√2 - 1/√2 i) (2cis40°)^6 = 2^6 cis240° = 64 (-1/2 - √3/2 i) you can make those into a+bi form, but you need to review deMoivre's formulas
*April 18, 2016*

**Math**

√(2x-4) + 5 = 7 √(2x-4) = 2 2x-4 = 4 x = 4 check: √(8-4) + 5 = 2+5 = 7
*April 18, 2016*

**Pre calculus**

just review your trig definitions cotx * secx = cosx/sinx * 1/cosx = 1/sinx
*April 18, 2016*

**algebra**

5n+10d+25q = 780 n+d+q = 46 n+d = q-2 Now just solve.
*April 18, 2016*

**algebra**

if $x at 6%, the rest (2150-x) is at 8%. So, now we have .08(2150-x) = 22+2(.06x) now just crank it out.
*April 18, 2016*

**math**

(a) find t where 1.011^t = 2
*April 18, 2016*

**Math (Elementary Algebra)**

2x^2 + 3xy - 4y^2 now substitute your values for every x and y: 2(2^2) + 3(2)(-4) - 4(-4)^2 = 2(4) - 24 - 4(16) = 8-24-64 = -80
*April 18, 2016*

**calculus**

I assume you are looking for the area. A straightforward integration will give the algebraic area, since the curves cross at x=1, and the area changes sign. ∫[-2,2] (-x^2+6x+2)-(2x^2+9x-4) dx = ∫[-2,2] -3x^2-3x+6 dx = 8 However, to get the geometric area, you need ...
*April 18, 2016*

**Calculus**

the curves intersect at 𝜋/6 and 5𝜋/6, so the volume, using shells, is v = ∫[π/6,5π/6] 2πrh dx where r=x and h=sinx - 1/2 v = ∫[π/6,5π/6] 2πx(sinx-1/2) dx = π^2(√3 - π/3) using discs, it's tougher: v...
*April 18, 2016*

**Algebra**

because the discriminant (b^2-4ac) is negative.
*April 17, 2016*

**math**

since time = distance/speed, 45/(x-2) + 45/(x+2) = 14
*April 17, 2016*

**Math **

you haven't paid much attention to the solutions to your previous problems. Review the distributive property. Then you will see that -2r(8r+5) = -2r(8r) + (-2r)(5) = -16r^2 - 10r
*April 17, 2016*

**math**

the height h is given by h/517 = tan 16°
*April 17, 2016*

**Math **

if you say so. Good luck with that.
*April 17, 2016*

**Math **

I showed the steps in the solution, not three answers. See those "=" signs? That means that each line is equal to the one above it, not a new answer. It just shows the way to simplify the expression.
*April 17, 2016*

**Math **

EXCUSE ME??? I showed you the answer. None of the choices matches. Check for typos in the problem or the answers offered.
*April 17, 2016*

**Math **

huh? really? 2a(a^2+4a) = 2a(a^2) + 2a(4a) = 2a^3 + 8a^2 check for typos...
*April 17, 2016*

**Stats**

you can play around with Z table stuff at http://davidmlane.com/hyperstat/z_table.html
*April 17, 2016*

**mathematics-need help urgently please**

v = x^2h, so h = 1000/x^2 a = 2x^2 + 4xh = 2x^2 + 4000/x da/dx = 4x - 4000/x^2 = 4(x^3-1000)/x^2 so, da/dx = 0 when x=10 a = 2*100 + 4*10*1000/100 = 600 as usual, area is minimum when the shape is a cube.
*April 17, 2016*

**PRECALC**

you know that anything more complicated than a quadratic is tough, so look for low-hanging roots: ±1,±2,±3. A little synthetic division yields P(x) = (x-3)(x+1)(x^2+1) now it's easy.
*April 17, 2016*

**precalc**

of course -b/2a does not work. It's not a quadratic. Furthermore, x = -b/2a gives the location of the vertex of a quadratic, not the roots. You know that any rational roots must be among ±1,±2,±5,±10 A little synthetic division shows that p(x...
*April 17, 2016*

**precalc**

d: the arccos has principal vales from 0 to π. cos(-4π/3) = -1/2 cos^-1(-1/2) = 2π/3 f: cos(13π/12) = -cos(π/12) = -x arccos(-x) = π-arccos(x) = 11π/12 The others look good. Be careful with the principal values stuff.
*April 17, 2016*

**dividing fraction with brackets**

5/6 - 2(-1 3/4)/(5 1/5) 5/6 - 2(-7/4)/(26/5) 5/6 - 2(-7/4)(5/26) 5/6 + 35/52 (5*32 + 35*6)/312 470/312 235/156
*April 17, 2016*

**Math**

r:b = 3:2 = 9:6 b:g = 3:7 = 6:14 r:b:g = 9:6:14 assuming none of the ones removed were red, 1/4 (9x+6x+14x - 7) = 9x Hmmm. I get x = -1 better double-check my math and the problem.
*April 17, 2016*

**maths**

by definition, x = arccos(3/5) of course, x might be in quadrants I or IV. cos(.9273) = 0.6 cos(5.3559) = 0.6 x = 2kπ ± 0.9273
*April 17, 2016*

**Trigonometry**

Draw your triangle in standard position. Then you have r=5 secθ = r/x = 5/-3
*April 17, 2016*

**maths**

The first digit must be 1,2 or 3 That leaves 4 digits to shuffle for the others. So, the total number is 3 * 4! = 72
*April 17, 2016*

**calculus help**

or, you can expand cos^10(x) as combinations of single powers of cosines: 512 cos^10(x) = 126 + 210cos(2x) + 120cos(4x) + 45cos(6x) + 10cos(8x) + cos(10x) those terms are easy to integrate. They come from repeated use of cos(2x) = 2 cos^2(x)-1 cos(4x) = 2cos^2(2x)-1 and so on.
*April 17, 2016*

**calculus help**

This has to be done in several steps using integration by parts. To see how it works, take a look at https://en.wikipedia.org/wiki/Integration_by_reduction_formulae
*April 17, 2016*

**Calcus**

oh. right. you want to use calculus. f' = 2x+k f'=0 at x = -k/2 f(-k/2) = k^2/4 + k(-k/2) + 2 = k^2/4 - k^2/2 + 2 = -k^2/4 + 2 we want the minimum to be 1, so -k^2/4 + 2 = 1 k^2/4 = 1 k^2 = 4 k = ±2 as above
*April 17, 2016*

**Calcus**

try completing the square. x^2+kx+2 = x^2 + kx + (k/2)^2 + 2 -(k/2)^2 = (x + k/2) + 2 - k^2/4 Now you have the vertex form of the parabola, with the vertex at x = -k/2. At that point, the minimum is 2 - k^2/4 So, now just set 2 - k^2/4 = 1 k^2/4 = 1 k^2 = 4 k = ±2 f(x...
*April 17, 2016*

**HUNGER GAMES**

google is your friend
*April 17, 2016*

**algebra**

oops. |2n+1| = (2n+1) or -(2n+1) if -(2n+1) = 19 -2n = 20 n = -10 check: |(3(-10)+1-(-10)| = |-30+1+10| = |-19| = 19
*April 17, 2016*

**math**

I think it's supposed to read "1/3 of them are blue." 1/3 of 21 = 7
*April 17, 2016*

**Calculus**

as usual, the volumes can be done using shells (v = 2πrh) or discs (washers) (v=πr^2), both multiplied by the thickness (dx or dy). I'll show both integrals (i) v = ∫[0,ln3] π(e^(2x))^2 dx = 20π v = π(1^2)(ln3) + ∫[1,9] 2πy(ln3 - 1...
*April 17, 2016*

**math**

that's alpha and beta. I'll use x and y for ease of typing. since the angles are complementary, cos(x) = sin(y) cos(x)*cos(y) = sin(y)*cos(y) = 1/2 sin(2y) since sin has maximum value of 1, ...
*April 17, 2016*

**MATHS**

times D w by D h by D l
*April 17, 2016*

**math**

1 - 3/7 = 4/7
*April 17, 2016*

**Math**

3(-1) / ((-1)^2-(-1)-12) = -3/-10 = 3/10 = 0.3 you are correct
*April 16, 2016*