Saturday
December 10, 2016

Posts by steve

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
42
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

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