Question

find the exact value of : cos(2 arctan(4/3))

Answer 1

2 tan^-1(4/3) gives us an angle between (-pi/2,pi/2)...

Answer 2

its a 4-3-5 triangle, I notice that

Answer 3

3-4-5....but same difference lol

Answer 4

the cos will equal 3/5, so 2(3/6) = 6/5

that might help us

Answer 5

cos(cos^-1(6/5)) sounds right

so cos(t) = 6/5 .... is that findable?

Answer 6

or is that our answer :)

Answer 7

to recap...for my own sanity:

cos(t) = x

t = 2 tan^-1(4/3)

t = 2 cos^-1(3/5)

t =2 cos^-1(3/5)


cos(2 cos^-1(3/5)) i now this is suppose to help me....

Answer 8

t/2 = cos^-1(3/5) might fit someplace

Answer 9

lol...i think i confused myself again

Answer 10

oh
i figured it out
the answer is -7/25, thanks for your help