Saturday

December 10, 2016
Total # Posts: 47,046

**Math, Precalc**

can't see your diagram, but consider the vectors representing the diagonals. If it's a unit cube, they might be joining (0,0,0) and (1,1,1) = <1,1,1> (1,1,0) and (0,0,1) = <-1,-1,1> (1,0,0) and (0,1,1) = <-1,1,1> ... Now just take the dot product of ...

*November 6, 2016*

**Calculus**

Actually, since f(x)=0 at all those points, we can use Rolle's Theorem, which is just a special case of the MVT were f(a) = f(b) on the interval [a,b]. Both theorems state that f'(c) exists with c in (a,b) such that the tangent is horizontal. That is, f'(c)=0, ...

*November 6, 2016*

**Math-Trigo**

Just draw your 5-12-13 triangle in standard position cot(90-A) = tan(A) = y/x = -12/5

*November 6, 2016*

**physic**

if 30°, then just find t when the height is zero: 30*sin30° t - 4.9t^2 = 0

*November 6, 2016*

**math**

Oops. adding the equations eliminates y. 7x = 28 ...

*November 6, 2016*

**math**

You meant: I can't; help me. 5x-2y = 14 2x+2y = 14 ------------- add the two equations 4y = 28 I expect that you can handle it from here, eh?

*November 6, 2016*

**Math**

6+2x=24

*November 6, 2016*

**math**

recall that a regular hexagon has sides equal to the circle's radius.

*November 6, 2016*

**calculus - PS**

#1 is not quite so amazing if you recognize that if a = tan(u) x = tan(v) y = arctan(tan(u+v)) = u+v y' = v' ...

*November 6, 2016*

**calculus**

recall that if y = arctan(u) y' = 1/(1+u^2) u' y=arctan(a+x/1-ax) y = 1/(1+((a+x)/(1-ax))^2) * (1+a^2)/(1-ax)^2 = ... amazing! y=(e^x-e^-x)/(e^x+e^-x) = tanh(x) ...

*November 6, 2016*

**Science**

brain

*November 6, 2016*

**math**

(50/4)*(4-1) = 37.5

*November 6, 2016*

**Physics**

step 1: what is the volume of the cube of ice? step 2: find out how much water is produced when the ice melts. It will decrease in volume by some percentage.

*November 5, 2016*

**Pre-Calculus**

It's the length of u in the direction of the unit vector v/|v|, so u • v/|v|

*November 5, 2016*

**Algebra 2**

log(30,8) = log8/log30 Since the base on the right does not matter, we can use base 10, giving us 3log2/(log2+log3+log5) = 3c/(c+b+a)

*November 5, 2016*

**physics**

volume(cm^3) = mass(g)/density(g/cm^3) so plug in your numbers. I assume you can find the side of a cube, given its volume. (By the way, the length is cm, not cm^3!)

*November 5, 2016*

**algebra**

PV=kT, so PV/T=k is constant. o, you need V such that 30V/330 = 35*20/350 V/11 = 2 V = 22

*November 5, 2016*

**chem.**

If there are x moles of Kr, then there are 2x moles of Ar. Since the number of moles has increased by a factor of 1.47/1.26, 2x+x+.3 = 3x(1.47/1.26) x = 0.6 So, there were originally 1.2 moles of Ar, making the final amount 1.5 moles.

*November 5, 2016*

**Advanced Physics**

Since you don't give any time values, there's no way to figure displacements. Also, the vector does not move; some object does. Also, your explanation is odd. How do you turn southeast? You can turn 30 degrees clockwise, which is toward the SE. Or do you mean that the ...

*November 5, 2016*

**Pre cal**

recall that vertical asymptotes occur when the denominator is zero and the numerator is not. Removable discontinuities are where the fraction is 0/0 Horizontal asymptotes are what happens when x gets huge. f(x) = (x-3)(x+2) -------------- x^2 (x-4) get it now? If not, where do...

*November 5, 2016*

**Math**

If he had d dimes, then he had 3d nickels. So, add up the value of each group of coins: 10d + 5(3d) = 100

*November 5, 2016*

**math**

you can play around with Z table stuff here: http://davidmlane.com/hyperstat/z_table.html

*November 5, 2016*

**algebra**

x = kF x/F is constant. You want F such that 9/F = 10/8

*November 5, 2016*

**Algebra**

or, assuming the usual carelessness with parentheses, (4r+12)/8 = (5r-20)/5 r/2 + 3/2 = r - 4 r = 11

*November 5, 2016*

**math**

24*2+36 = 84 kg flour 50 kg sugar So, now you can figure how many packets of each were made, and thus how many got both.

*November 5, 2016*

**math- Trigonometry**

Look. If cos(x) = 0.8641, you use your cos^-1 button to get x. cos^-1(.8641) = 30.22° sin 30.22° = 0.5033 So, since they gave you the answer in two different ways, as well as a sanity check to see why it makes sense, what is your work, which produces something else? If...

*November 5, 2016*

**sir-reiny-steve help**

assuming all were shot somewhere, (42+43+32) - (5+8+6) + x = 100 Review your Venn diagram material to see why.

*November 5, 2016*

**Math gemetry**

apparently, not to study geometry with a social worker!

*November 5, 2016*

**Math**

#1 ok #2 you have solved 3n = -12 #3 You have solved b/9 = 19 #4 You have solved y-1.8 = 3.18 Did you not check your answers to see whether they actually worked?

*November 5, 2016*

**Math 062**

5642/403 * 3

*November 5, 2016*

**Advance function**

just think back to your Algebra II. Terms of a GP have a common ratio, so tanx/sinx = sin2x/tanx 1/cosx = = 2sinx*cosx * cosx/sinx ...

*November 5, 2016*

**Math**

3 - 1 of each color

*November 5, 2016*

**Math**

suppose there were 40 cows = 160 feet so, you would need 32/2 = 16 fewer cows: 24. The 32 feet would be made up with 16 hens.

*November 5, 2016*

**Adv function**

I think you misplaced a minus sign. Fix it and think "difference of squares"

*November 5, 2016*

**Calculus - huh**

Not what I expected, but quite true. The equilateral triangle has area 4?3 < 8

*November 5, 2016*

**Calculus**

do some setup and I'm sure you will find that the problem is solved by a regular n-gon regardless of the number of sides. Just define the third side in terms of the included angle.

*November 5, 2016*

**Maths**

15.01 15.001 15.0001 17.999 17.99 17.9 I'm sure you can find many more

*November 5, 2016*

**math**

sin(a) cannot exceed 1. Fix your typo and repost.

*November 5, 2016*

**algebra**

.03x + .04y = 170 .04x + .03y = 180 now crank it out.

*November 5, 2016*

**mathematics**

Any point will have its x-coordinate reversed in sign.

*November 5, 2016*

**math**

get numbers add to get sum avg = sum/3 update max and min as the list is read in

*November 5, 2016*

**time speed and distance**

your turn to provide some ideas. We've done several of these for you by now.

*November 5, 2016*

**Maths**

v = pi r^2 h = pi r^2 r ... 2pi r (r+h) = 2pi r(r+h) = 1 ...

*November 5, 2016*

**Maths**

each 1cm layer of water has a volume of 30^2 * 1 = 900 cm^3 So, what's the total volume of the fish? Divide that by 900cm^3 to find how much the water level rises.

*November 5, 2016*

**math**

well, their combined rate is 720/4 = 180 mi/hr

*November 5, 2016*

**science**

convert to moles see how much H2SO4 remains after being neutralized by twice that many moles of KOH. Convert that back to moles/L

*November 4, 2016*

**Calculus Reimann Sum**

so, how did you do it? If the interval is [-2,3] then each interval has length 1, so I fail to see how you got the fraction.

*November 4, 2016*

**algebra 1**

5x-2 passes through (8,38) So, you need to subtract 40 so it goes through (8,-2)

*November 4, 2016*

**Calculus**

Note the sum. You have a2-a1 + a3-a2 + a4-a3 + ... + a21-a20 = a21-a1 = 2^21 - 2^1 There's really no reason to write the sum as you did. Since you know a_i explicitly, it would be better just to say 20 ? 2^(i+1)-2^i i=1

*November 4, 2016*

**Calculus - Special sum formulas**

see your other post. Repeating it does no one any good. Don't forget your Algebra I now that you're taking Calculus!

*November 4, 2016*

**Calculus - Special sum formulas**

Huh? You have the answer. Just simplify if you want: n(n^2-37)/3

*November 4, 2016*

**Pre-algebra**

no. all whole numbers are rational (fractions with denominator=1, as in 2/1, 4/1, etc.) There are lots of numbers that are not rational (irrational), like ?, ?3, ?5, etc. They cannot be expressed as the ratio of two integers.

*November 4, 2016*

**Calculus**

a = 24t+4 v = 12t^2+4t+11 s = 4t^3+2t^2+11t+15 so, s(9) = ?

*November 4, 2016*

**Calculus - Differential Equations**

oh come on. 0+C = -4/6 C = -2/3 -4/u = t - 4/3 u = -4/(t - 4/3) = 12/(4-3t)

*November 4, 2016*

**Calculus - Falling Body Problem**

it is well known that the equations are s(t) = 3000+75t-16t^2 v(t) = 75-32t So plug and chug Extra credit: derive those equations.

*November 4, 2016*

**Calculus - Differential Equations**

so, crank it out: 4 du = u^2 dt 4/u^2 du = dt -4/u = t+C now plug in (0,6) to get C.

*November 4, 2016*

**Tricky Math Question**

However, if you look at the graph for y = x^x the limit near zero is 1. limit x^x log(limit) = x*logx = logx/(1/x) use l'Hospital's rule: = (1/x) / (-1/x^2) = -x log(limit)=0, so limit=1

*November 4, 2016*

**Pre-Algebra**

right Although we're not really using the associative property. That would state that (2.25 • 23) • 4 = 2.25 • (23 • 4) All you did was evaluate the expression inside the parentheses and replace it with an equal value.

*November 4, 2016*

**Math**

well, the floor is 10x16 tiles in size, so ...

*November 4, 2016*

**ss**

well, surely you know that (a) N-S directions are latitude (b) N.A. is west of England...

*November 4, 2016*

**physics**

If ? is the angle upstream, then you have sin? = 2.5/7.3

*November 4, 2016*

**science**

y = tan? x - g/(2 (v cos?)^2) x^2 so plug in your numbers and solve for v when y(10) = 2

*November 4, 2016*

**MATHS**

which area? lateral, total, circular base? I'll assume the base. Volume = base_area * height

*November 4, 2016*

**Physics**

(v^2 sin2?)/g = v^2 sin^2?/g 2sin? cos? = sin^2? 2cos? = sin? tan? = 2

*November 4, 2016*

**Physics**

result of downward and sideways motion.

*November 4, 2016*

**Physics**

a = 7.2km/hr-s s = 1/2 * 7.2 * (10/3600)^2 + (72*20/3600 - 1/2 * 3.6 * (20/3600)^2) = .4km = 400m

*November 4, 2016*

**Math**

4 * 5 1/2 * 2 1/2 = 55 ft Extra credit: How many pieces is that? Are leftover portions after cutting to be used as needed?

*November 4, 2016*

**help help help sir steve**

Well! The method is similar to long division. If you have learned how to do square roots by hand, this method is just an extension of tat same algorithm. But to explain it here is not a good use of resources. If you google cube root by hand you will find many articles and ...

*November 4, 2016*

**math**

their areas are in the ratio (2/5)^2

*November 4, 2016*

**math**

the map figure has area a = (5+2)/2 * 4 = 14 cm^2 The area is 14 * 500^2 cm^2 Now just convert that to m^2

*November 4, 2016*

**maths**

Looks like 7 to me, since it is the only number unused in the other phrases, which also mention bring and apple.

*November 4, 2016*

**Math**

585 = 0.9 x

*November 4, 2016*

**Science**

how many moles? M = moles*(1000/100)

*November 4, 2016*

**Math**

see the related questions below, and use your numbers.

*November 4, 2016*

**mathe arithmetic progression**

sorry - fix your typo, then we can get somewhere.

*November 4, 2016*

**communications**

communications

*November 4, 2016*

**Algebra 2**

f(x) = 4 for 0 <= x < 3 f(x) = 6 for 3 <= x < 6 ...

*November 4, 2016*

**Math**

90 * 30/5

*November 3, 2016*

**Math**

((10-3)+(8-3))*x = 60

*November 3, 2016*

**Physics**

surrounding air is humid

*November 3, 2016*

**Calculus**

so, you seem to have the diagram down. Now just define the cost function and minimize it. What do you get? Is your 30-60-90 triangle you final answer, or some intermediate stage?

*November 3, 2016*

**Finite math**

there are 2^3 = 8 subsets of S. see where that takes you.

*November 3, 2016*

**calculus**

see related questions below.

*November 3, 2016*

**Math**

If he had x lbs of flour, 2/5 x = 16 x = 40 so now you can answer the question...

*November 3, 2016*

**Math**

well, 15-2 = 13 see what you can do with that.

*November 3, 2016*

**Math**

looks like each topping costs $1.50 so ...

*November 3, 2016*

**precalculos**

for each part, just divide the total cost by how many calculators: C(x)/x

*November 3, 2016*

**Adv function**

sin(7x) = sin(x+6x) = sinx cos6x + cosx sin6x = sinx*cos(2*3x) + cosx*sin(2*3x) ...

*November 3, 2016*

**Math**

assuming no friction, consider the cases of 0°: 0 force 90°: full weight Looks like weight * sin(angle)

*November 3, 2016*

**Math-PreCalc**

Draw a diagram. The resultant is just the hypotenuse of the triangle with u and v as legs. The angle t with u is tan(t) = 30/47

*November 3, 2016*

**Calc**

see related questions below

*November 3, 2016*

**Calculus - YES! @Reiny**

*whew* what a relief that we agreed!!

*November 3, 2016*

**Calculus**

what, no effort since you last [posted this problem? Most of it is just geometry. If the radius is r and the cylinder length is h, then 4/3 ? r^3 + ?r^2 h = 1600 so h = (4800 - 4?r^3)/(3?r^2) = 1600/?r^2 - 4r/3 If the sides cost $1/ft^2, then the ends cost $2/ft^2, so the cost...

*November 3, 2016*

**Math**

total:red = 14:3 12/20 = 3/5 = red:yellow 8 hours is 4 times as long as 2 hours, so it will go 4 times as far. Your answer is the distance gone in 2/4 hours. It should have been immediately clear that your number was too small, since the plane had more time. Keep your ratios ...

*November 3, 2016*

**Math**

Just do what you always do to isolate one variable. c/xy = (3d/4-ab) c/xy = (3d-4ab)/4 4c/(3d-4ab) = xy x = 4c / y(3d-ab)

*November 3, 2016*

**Math**

clearly, since there are asymptotes there, g' is undefined. It might be increasing or decreasing near the asymptote, but g'(-2) and g'(4) are undefined.

*November 3, 2016*

**Math**

correct. It has to be continuous to be differentiable.

*November 3, 2016*

**Algebra**

yes.

*November 3, 2016*

**Calculus**

Great. No matter which way you do it, you have to divide the region into two parts because of the boundary changes. So, the area could be either ?[0,1] (x - x/8) dx + ?[1,2] (1/x^2 - x/8) dx = 3/4 ?[0,1/4] (8y - y) dy + ?[1/4,1] (1/?y - y) dy = 3/4

*November 3, 2016*