Wednesday

November 25, 2015
Total # Posts: 35,775

**Trigonometry**

poke around a bit and you will find proofs that if the tangents intersect at an angle θ, then if the circles have radii r and R, and the centers are d apart, then sinθ = √(2r^2R^2 + 2r^2d^2 + 2R^2d^2 - r^4 - R^4 - d^4)/(2Rr) so, plug in your numbers
*October 24, 2015*

**MATH**

(−2x^−3 y^−2 )^−1 = -1/2 x^3 y^2 1/(x^3y^3z^3 )^−4 = x^12 y^12 z^12 now multiply and you get -1/2 x^15 y^14 z^12
*October 24, 2015*

**astronomy**

(4*10^33) / 4π(2*7*10^10)^2 = 3/(4π*4*7^2) * 10^13 = 0.001218 * 10^12 = 1.218 * 10^9 You plugged in the radius, not the diameter.
*October 24, 2015*

**Physics**

a = (42.3/13.8) m/s^2 weight is now 70.2(g+a)
*October 24, 2015*

**trignometry**

graphs can be done at wolframalpha.com or many other sites.
*October 24, 2015*

**trignometry**

your equation is (2cos4θ - 1)(cos4θ + 3) = 0 so, find all the angles θ where cos4θ = 1/2 or cos4θ = -3 Note that cos4θ has period pi/2, so you will have more solutions than normal, since the domain covers 4 periods.
*October 24, 2015*

**trignometry**

sinx (1+2cosx) 0 so, sinx = 0 or cosx = -1/2
*October 24, 2015*

**trigonometry**

putting everything i nterms of sin and cos, you have 2sinx + cosx/sinx - 1/sinx = 0 (2sin^2 x + cosx - 1)/sinx = 0 so, x where sinx=0 must be excluded from the domain. (2 - 2cos^2 x + cosx - 1) = 0 2cos^2 x - cosx - 1 = 0 (2cosx + 1)(cosx - 1) = 0 so, you need cosx = -1/2 or ...
*October 24, 2015*

**Pre- Algebra**

what is the difference between 10 and 5? same thing here.
*October 24, 2015*

**Qibing**

tax benefits
*October 24, 2015*

**addition fraction**

use a common denominator of 60 and then add 'em up.
*October 24, 2015*

**AP Physics**

the trajectory article at wikipedia gives a good discussion of this kind of problem.
*October 24, 2015*

**math**

13 cards in each suit. 1st card has to be some suit. Given that, P(same,same) = 12/51 * 11/50
*October 24, 2015*

**epcc**

0.80 of course. Now, if you want the mass, that is 0.8 * (molar mass of compound) Add up all the atomic masses involved in the molecule to get the molar mass.
*October 24, 2015*

**physics**

see the wikipedia entry for trajectory for a good discussion.
*October 24, 2015*

**Physics**

Since F=ma, the 0.2N friction causes a deceleration of .2/.03 = 1.67 m/s^2 so, its speed and position are described by v = 36 - 1.67t s = 36t - 0.83 t^2 You can find t when v=0 (stopped) and use that value to find the stopping position. Not uniform motion, but uniform ...
*October 24, 2015*

**MATH - sheesh!**

surely a calculator is quicker than posting and waiting. Just saying...
*October 24, 2015*

**math**

dN = .03N dt you have N=100 and dt=0.1 plug and chug N(4.1) ≈ 100 + dN
*October 24, 2015*

**C++programming**

I must say, you got a lotta nerve. Don't expect anyone to write this for you. But we will take a look at what you have. On the other hand, the compiler will do that for you, and simply running your code will verify its function. A bare-bones version of this cannot be more ...
*October 24, 2015*

**use auxilary verb in bracket**

i do wish to take a break. i'm so tired.
*October 24, 2015*

**math**

the 2nd line says that a^2+b^2 = 5ab a^4+b^4 = (a^2+b^2)^2 - (2ab)^2 That should help, but I cannot decipher the ~A character. Go for it.
*October 24, 2015*

**Calculus 1**

f(0) = 0 f(16) = 4 slope of secant: 1/4 f' = 1/2√x 1/2√x = 1/4 2√x = 4 x = 4 which is in [0,16] verify at http://www.wolframalpha.com/input/?i=plot+y%3D%E2%88%9Ax%2C+y+%3D+%281%2F4%29%28x-4%29+%2B+2+for+0+%3C%3D+x+%3C%3D+16
*October 24, 2015*

**Math**

product of a number and six: 6x 6 decreased by n is 6-n, so you wind up with 6 - 6x = 20
*October 24, 2015*

**math**

if the mean was 50, then the total was 100*50 Now, the mean is (100*50 + 10)/50 = 50.2 The median is the same, since the place of the middle value has not changed. This must be so, since it is less than 100, and only the greatest value has changed.
*October 23, 2015*

**Math**

that's better
*October 23, 2015*

**Math**

cannot be. |sin(x)| <= 1 for any x. 7pi/6 - pi/3 = 2pi/3 so, what is sin(2pi/3) = sin(pi/3) ?
*October 23, 2015*

**Math**

of course not. If 1-u = 1, then u=0. Unless one of those tan values is zero, the assertion is false.
*October 23, 2015*

**Algebra**

For x ft^2 of wall, you want 4*30 + 1.10x < 4*24 + 1.20x
*October 23, 2015*

**Trigonometry**

Draw a diagram. If the tip of the shadow is x feet horizontally away from the tree of height x, we have x/31 = cos 7° (h + 31*sin7°)/x = tan 59° I get h = 47.4 ft
*October 23, 2015*

**Algebra 2**

no. You just keep multiplying by 1/2.
*October 23, 2015*

**Math**

use your calculator. sin 26.56° = 1/√5 Use your arcsin or sin^-1 button. Or use an online calculator.
*October 23, 2015*

**Math**

you know that if v is the initial upward velocity, v-9.8*0.67 = 0 Plug that into the usual equation h(t) = 88 + 6.566t - 4.9t^2 Then check that h(3.18) = 0 Or, since a parabola is symmetric, you know that h(t) = a(t-0.67)^2 + 88 h(3.18) = 0, so a(3.18-0.67)^2 + 88 = 0 h(t) = -...
*October 23, 2015*

**Math**

plug in some values. After 5 steps, you will have 5 equations, which you can then solve as usual. For example, if x=3, 81a+27b+9c+3d+e = 6 and so on.
*October 23, 2015*

**Math**

well, g'=4x^3-15x^2+14x-3 where is g'=0?
*October 23, 2015*

**shahabdulatif science**

clearly, the acceleration is ((20-10)m/s)/((5-0)s) = 10/5 = 2 m/s^2 so at t-3, v = 10-3*2 = 4 m/s
*October 23, 2015*

**Physics**

only the horizontal force does any work. Find the x-component of the force, then recall that work = force * distance
*October 23, 2015*

**Physics**

work = force * distance, so that would be 50 m-lb not the usual units, but I'll let you decide what you want to use.
*October 23, 2015*

**physics -plz help**

1) KE = 1/2 mv^2 = (1/2)(950)(100^2) kg-km^2/hr^2 Not the usual units, but you can do the conversion. 2) 1300 √(20^2/160) 3) a = F/m = 6000/1200 = 5 So, it takes 30/5 = 6 seconds to stop. s = 30t - 5/2 t^2 where t=6
*October 23, 2015*

**Chemistry: gas law**

first change everything to moles, and then recall that at STP, 1 mole occupies 22.4L of volume.
*October 23, 2015*

**physics**

moving with constant velocity (slow enough that air resistance is not a factor)
*October 23, 2015*

**Math**

(7/2) * £6.30 (7/2) * 400 (24/18) * 570
*October 23, 2015*

**Math**

(25/20) * 10
*October 23, 2015*

**Math**

well, you can rewrite your equation as sin x = ±1/√5 so, find your reference angle, and use it in each quadrant.
*October 23, 2015*

**physics**

for any momentum to instantly (not instantaneously!) go to zero, there must be infinite deceleration.
*October 22, 2015*

**Physics**

conserving momentum, (38.2+26.6)v = -5.90*10
*October 22, 2015*

**Honors pre algebra**

Well, you know that 1/6 = 0.16666... so, you have 4 1/6
*October 22, 2015*

**History**

Thank you
*October 22, 2015*

**History**

The transition to a global economy has increased "what" within the U>S>? a- income inequality b- educational opportunity c- income equity d- buying power My answer is a
*October 22, 2015*

**math**

-e/5 - 12 = -3 -e/5 = 9 -e = 45 e = -45
*October 22, 2015*

**Algebra**

well, you could solve your result for nx. It is correct, by the way.
*October 22, 2015*

**Calculus-Steve**

Oops. My bad. I missed f(x). You are correct.
*October 22, 2015*

**Algebra**

just clear the fractions and remove the parentheses. Then it's easy: r(g+s) = gs rg+rs = gs rs = g(s-r) g = rs/(s-r)
*October 22, 2015*

**Algebra**

since the perimeter of a square is 4 times a side, we clearly have 4x+4 + 5x-3 + 17 = 4(3x) Now solve for x, and the side is 3x.
*October 22, 2015*

**Science/physics**

AxB has to form a right-handed system. If angles greater than 90 degrees are involved, that does not hold.
*October 22, 2015*

**math**

change to fractions, find the common denominator, then add: 11/4 + 17/5 = 55/20 + 68/20 = ...
*October 22, 2015*

**Intellectual Academy**

the weight is 500N 80% efficiency means that 1/.8 = 1.25 the weight is needed.
*October 22, 2015*

**algebra**

inaccurate ruler.
*October 22, 2015*

**Math**

discover the common denominator, then add the numerators. For example, 2 3/4 + 1 2/3 - 3 2/7 = 11/4 + 5/3 - 23/7 The common denominator is 4*3*7, so that makes things = 11*3*7/84 + 5*4*7/84 - 23*4*3/84 = 231/84 + 140/84 - 276/84 = 95/84 = 1 11/84
*October 22, 2015*

**Calculus**

∫[0,2] (x^2+2x+2) dx = 1/3 x^3 + x^2 + 2x [0,2] = 8/3 + 4 + 4 = 32/3 It would be nice for you to show your work...
*October 22, 2015*

**math**

1+6=7, so 6/7 have just the symptoms. 40 * 6/7 ≈ 42*6/7 = 36
*October 22, 2015*

**edagahamus com.sec.school**

check out Vieta's formulas.
*October 22, 2015*

**Barrles**

clearly there are no solutions if c >= 5.
*October 22, 2015*

**algebra**

so, just follow the normal steps. No mystery here. R(a+b) = ab Ra+Rb = ab a(R-b) = -Rb a = Rb/(b-R) or, note that 1/R = (a+b)/ab 1/R = 1/b + 1/a 1/a = 1/R - 1/b 1/a = (b-R)/Rb a = Rb/(b-R)
*October 22, 2015*

**Simultaneous equation i nee help find x,y**

Is that y^(2-x) = y^2 / y^x or y^2 - x? Makes a big difference Either way, graphic or numeric tools will need to be used.
*October 22, 2015*

**Calculus III**

so, did you use the formula? What did you get?
*October 22, 2015*

**Math 5**

Sorry - can't be done. 13 is prime, so since all the operations except the +3 are multiply/divide, the +3 must be on its own. That means that (12 ÷ 2 ∙ 9 ÷ 3 ∙ 2) + 3 = 13 and 12 ÷ 2 ∙ 9 ÷ 3 ∙ 2 = 10 But, 5 is a factor of...
*October 22, 2015*

**geometry**

clearly the edge is √81 = 9. So, what is 9^3 ?
*October 22, 2015*

**ahisco**

T8-T4 = 4d, so d=5 T8 = T4/2 (a+7d) = (a+3d)/2 a+35 = (a+15)/2 2a+70 = a+15 a = -55
*October 22, 2015*

**math**

80-68 = 12
*October 22, 2015*

**math**

Assuming a geometric series, Sn = a(r^n-1)/(r-1) So, since 2^(n+3)-8 = 2^n*2^3 - 8 = 8*2^n-8 = 8(2^n-1) Looks like a=8 and r=2. S7 = 8*2^6 = 512
*October 22, 2015*

**math**

for the derivative, remember the chain rule. In this case, u=sinx and f(u) = u^2, so f'(x) = 2u u', as below. f = 6 sin^2 x − 6 cos x f' = 12sinx cosx + 6sinx (a) max/min where f'=0 6sinx(2cosx+1) = 0 f" = 6cosx + 6cos(2x) max if f" < 0 min ...
*October 21, 2015*

**Math**

figure earth's circumference. It will take 1/5 that many hours to walk it. It will take 1/(5*24) = 1/120 that many days to walk it.
*October 21, 2015*

**Math**

a cone has 1/3 the volume of a cylinder with the same base and height.
*October 21, 2015*

**Related Rates Calculus**

If the man's distance is x, and the shadow's length is s, and the light is at height h, then using similar triangles, 1.8/s = h/(x+s) or, 1.8x + 1.8s = hs 1.8x = s(h-1.8) 1.9 dx/dt = (h-1.8) ds/dt Now plug in your numbers and solve for h.
*October 21, 2015*

**math**

1/a + 1/b = 1/12 So, if A left after n days, A&B did n/12 of the work. 20/b = 1 - n/12 240 = 12b - nb b = 240/(12-n) so, 1/a + (12-n)/240 = 1/12 240 + (12-n)a = 20a a = 240/(8+n) I agree the question is confusing. The exact conditions seem ambiguous.
*October 21, 2015*

**Vector resultant angles help**

see related question below.
*October 21, 2015*

**Math**

C has a typo. One of the terms should be x^2, I expect. If so, then C is just a parabola, and its minimum cost is at the vertex.
*October 21, 2015*

**math**

no table. But multiply each amount by its probability, and add up the results.
*October 21, 2015*

**Algebra 2**

anything that can be counted (raindrops, population, etc.) is discrete. Things that must be measured (water level, temperature, etc.) are continuous.
*October 21, 2015*

**Vector resultant angles**

well, its angle θ is tanθ = 12/-9 did you actually try drawing a diagram? I assume you can convert from the conventional trig angles to compass directions ...
*October 21, 2015*

**Algebra**

clearly the smaller wheel has 2/3 the diameter of the larger wheel. So, it has 2/3 * 18 = 12 teeth. So, what is 7/12 of its circumference?
*October 21, 2015*

**Math**

40 is not the answer. She wants to read at least 200 pages, so she needs to read at least 40 pages per day: p >= 40
*October 21, 2015*

**Math**

5p >= 200 p >= 40
*October 21, 2015*

**Algebra I**

This is the formula for compound interest on a fixed deposit. It is not the formula for loan amortization, which takes into account the declining balance. Better check you formula list. However, if that's the formula you were supposed to use, you did it right.
*October 21, 2015*

**math**

If the original width is w, then the length is 2w-3. After the changes, 2((2w+3)-2 + w-1) 24
*October 21, 2015*

**ai**

240/3.5 mi/hr
*October 21, 2015*

**math**

there's no equation. You just want to factor out a common value (3) to illustrate the distributive property. 3w+18 = 3*w + 3*6 = 3(w+6)
*October 21, 2015*

**Geometry**

If the interior angles are x and y, x+y=90 (180-x)/(180-y) = 13/14 Now find x and y and pick the smaller.
*October 21, 2015*

**math**

x = 150/3
*October 21, 2015*

**Math**

looks good to me. but why did you not just write 30.3/10 ?
*October 21, 2015*

**features stars**

A∪B = {1,3,5,7,9}∪{1,2,3,4,5,6} = {1,2,3,4,5,6,7,9}
*October 21, 2015*

**Trigonometry**

as always, draw a diagram. Since the front is 5' taller than the back, the angle you want is θ, such that tanθ = 5/11
*October 21, 2015*

**trig**

a complete turn of the hoist is π ft a complete turn is 360° So, the hoist turns through (2.6/π) * 360°
*October 21, 2015*

**Trig**

The angular speed is (2π / 7.6896*10^6) rad/s
*October 21, 2015*

**Trig**

as always, draw a diagram. You can easily see that the length w is (190-30)/w = sin 39°
*October 21, 2015*

**Calculus i need help plz plz**

∫(sinx cosx)/(a^2 cos^2(x) + b^2 sin^2(x)) dx well, let's see. a^2 cos^2(x) + b^2 sin^2(x) = a^2 cos^2(x) + a^2 sin^2(x) + (b^2-a^2)sin^2(x) = a^2 + (b^2-a^2) sin^2(x) so, if u = a^2 + (b^2-a^2) sin^2(x) du = 2(b^2-a^2) sinx cosx dx and your integral now becomes 1/2...
*October 21, 2015*

**math**

start with x spend 2 on magazine, leaving x-2 spend (x-2)/2 on shoes, leaving (x-2)/2 spend ((x-2)/2)/2 leaving (x-2)/4 (x-2)/4 = 12 x = 50 check: start with 50 spend 2, leaving 48 spend half, leaving 24 spend half, leaving 12
*October 21, 2015*

**algebra 2**

so, what is confusing about using the quadratic formula? h^2 + 5h - 295 = 0 h = (-5±√(5^2 + 4*295)]/2 not so bad, eh?
*October 21, 2015*

**Math**

1+i^4 = 1+4i+6i^2+4i^3+i^4 = 1+4i-6-4i+1 = -4 or, 1+i = √2 cis 3π/4 so, (1+i)^4 = 4 cis3π = -4 I guess you can take it from there, right?
*October 21, 2015*

**math**

If x is at 6%, then the rest (12600-x) is at 8%. So, add up the interest: .06x + .08(12600-x) = 864.00
*October 21, 2015*