Posted by Rox on .
It is given that sin(θ)=1/√15. In addition, a and b are coprime positive integers such that cos(2θ)=a/b. What is the value of a+b?

maths 
Reiny,
cos 2Ø = 1  2sin^2 Ø
= 1  2(1/15) = 1  2/15 = 13/15 = a/b
and since a/b is in lowest terms
a = 13, b=15
so a+b = 28