Question

Find cos2θ
if sinθ=5/13
.

Answer 1

`\sf\\\textsf{We have,}\\cos2\theta = 1-2sin^2\theta\\or,\ cos2\theta=1-2((5)/(13))^2\\\\or,\ cos2\theta = 1-2((25)/(169))\\\\or,\ cos2\theta=1-(50)/(169)\\\\or,\ cos2\theta=(119)/(169)`