Mathematics

Under what operations are integers closed

Addition, subtraction and multiplication.

Can anyone help, please? simplify cos(x-y)cos y - sin(x-y)sin y

I keep coming up with cos x, but for some reason I dont think thats right. Can anyone verify?-Recall that cos A cos B - sin A sin B = cos(A + B) cos(x - y)cos(y) - sin(x - y)sin(y) = cos (x - y + y )

How to write an equation to express cost help please

storage building is planned which will have a rectangular base and a flat roof. The foundation (including floor) will cost $10 per square foot. The sides will cost $9 per square foot. The roof will co

How do I do this ln problem

5 - 4 ln x = 8 Some detail so I can figure out the others would be great.Thanks!-5 + ln x^-4 = 8 ln x^-4 = 3 x^-4 = e^3 x^-4 =(approximately) 20.08553692 log(base -4) x^-4 =(approximately) log(base -

CALCULUS: If f(x)=arctanx what is d/dx(f inverse x) when x = 1

Im off by the answer, what I did was that I switched x and y, took the derivative, plugged in one, found the f(x) value at x = 1, and solved for f(x). It hasnt gotten me the right answer, but it seeme

Find the area bound by curves.

Sketch the region enclosed by the given curves. Decide whether to integrate with respect to x or y. Then find the area of the region. 2y=3x y=5 and 2y+4x=7 Help please!!-Region enclosed by curves

Algebra equations problem! 10 points!

find the solutions to the equations: EQUATIONS 3X+3Y+3Z=18 X+3Y+3Z=10 X-3Y-4Z=0 POSSIBLE ANSWERS: A.X=-2Y=4Z=4 B.X=4Y=4Z=-2 C.X=5Y=3Z=9 D.X=5Y=3Z=3 PLZ xplain how u did it. thax!-haha stupid GINGER l

How to solve : x^2 < 9

As when u sq rt 9, u will get + , - 3. will the inequality sign change for -3? eg. x > -3 ? and x -x^2 (x - 3)(x + 3) x x > -3 -3 -You get the square root of 9, which canceled out the ^2. Therefo

Tan[2arccos(5/13)] help

can somebody please help me understand how to answer the problem: tan[2arccos(5/13)] do I need to use the double angle formula? thanks for your time! -Mike-Hi. Know your 5:12:13 triangles. Since the

Is x/(x-1)^2 integrable

yes, let u=x-1 orrewrite x/(x-1)^2 = 1/(x-1) + 1/(x-1)^2 , its very easy to integrate-Sure. The easy way is: ∫ (x/(x-1)^2) dx = ∫ (x-1 + 1) /(x-1)^2 dx = ∫ (1/(x-1)) dx + ∫ (1/(x-1)^2) dx = ln |x-1|

How to work out area of smaller triangle? Picture included

The area of the larger triangle is 5.6cm^2. I dont know how to work out the smaller one. I know you have to use this sign- 1/2 a b sin C But I dont know how to get C http://plixi.com/p/94442507 Th

Please help with this mean & standard deviation problem?!?!

Suppose that peoples heights ( in cm) are normally distributed, with a mean of 170 and a standard deviation of 5. We find the heights of 50 people. a). How many would you expect to be between 170 and

Can someone help please help me with this level of significance question (Statistics))

A random sample of 100 electric light bulbs produced by manufacturer A showed a mean lifetime of 1990 hours and a standard deviation of 90 hours. A random sample of 75 bulbs produced by manufacturer B

Help with math problem

Jeff and Kirk can build a 75 ft wall together in 4 hours. Because Jeff has more experience, he could build the wall by himself 3 hours quicker than Kirk. How long would it take Kirk, (to the nearest m

Identify the relation that is not a function

a. (d,2) (d,-1) (1,-3) b. (-2,d) (0,d) (1,-2) c. (-a,5) (a,1) (2,0) d. (a,2) (b,2) (c,2)-Answer is A because to be a function, it has to pass the vertical line test (draw a up and down line to find ho