2013 · Q44
If sin θ = (x²−y²)/(x²+y²), then which one of the following is correct?
Elementary MathematicsTrigonometry
- Acosθ=2xy/(x²−y²)
- Bcosθ=2xy/(x²+y²)
- Ccosθ=(x−y)/(x²+y²)
- Dcosθ=xy(x−y)/(x²+y²)
Explanation
cos²=1−sin²=4x²y²/(x²+y²)² → cos=2xy/(x²+y²). Answer B.