Trigonometry
posted by Jen .
How do i find
cos(2arctan(7/24))
Thanks.

Trigonometry 
drwls
A right triangle with sides of 7 and 24 has a hypotenuse of 25. The cosine of arctan 7/24 is 24/25 and the sine is 7/25.
Now use the formula
cos2A = cos^2A  sin^A
to arrive at
cos(2arctan(7/24))
= (24/25)^2  (7/25)^2 = 527/625
Respond to this Question
Similar Questions

tigonometry
expres the following as sums and differences of sines or cosines cos8t * sin2t sin(a+b) = sin(a)cos(b) + cos(a)sin(b) replacing by by b and using that cos(b)= cos(b) sin(b)= sin(b) gives: sin(ab) = sin(a)cos(b)  cos(a)sin(b) … 
Trigonometry
There is an arbitrary triangle with angles A, B, and C and sides of lengths a, b, and c. Angle A is opposite side a. How do I get the formulas: b * cos C + c * cos B = a c * cos A + a * cos C = b a * cos B + b * cos A = c Are these … 
Trigonometry
I need help with I just can't seem to get anywhere. this is as far as I have got: Solve for b arcsin(b)+ 2arctan(b)=pi arcsin(b)=pi2arctan(b) b=sin(pi2arctan(b)) Sub in Sin difference identity let 2U=(2arctan(b)) sin(ab)=sinacosbcosasinb … 
trigonometry
find without tables or calculator. (1) sin^2 (22 1/2) cos^2 (22 1/2) (2) sin 60 cos 30 + sin 30 cos 60 (3) cos(90y) = sin 56degree 47^i 
Trigonometry
Write equivalent equations in the form of inverse functions for a.)x=y+cos è b.)cosy=x^2 (can you show how you would solve) a.) x= y+ cos è cos è = xy theta = cos^1(xy) b.) cosy=x^2 cos(y) = x^2 y = Cos^1(x^2) 
Trigonometry
find cos (u+v) when cos v=(1/3) and sin u=(2/5) I found sin (v) to equal (sqrt8)/3 and cos (u)= (sqrt21)/5 
Trigonometry  find all x
Find all x such that 0 <= x <= pi/2 and sin^7 x + cos^7 x = 1. (Be sure to show that no other values of x satisfy the equation.) Well, I know sin^2 x + cos^2 x = 1, and that kind of looks like sin^7 x + cos^7 x = 1. I'm unsure … 
Math  Trigonometry
Let f(x) be a polynomial such that f(cos theta) = cos(4 theta) for all \theta. Find f(x). (This is essentially the same as finding cos(4 theta) in terms of cos theta; we structure the problem this way so that you can answer as a polynomial. … 
Calculus
Evaluate cos[2arctan(2)] Need step by step for this one. Thanks 
Trigonometry
Find the exact solutions of the equation in the interval [0, 2π). (cos 2x)  (cos x)=0