Question

已知sinθ>0,tanθ<0, 则化简√1-sin^2θ的结果为

cosθ
tan θ
- cos θ
±cos θ

Answer 1

sinθ>0,tanθ<0,
θ是第二象限角
1-sin^2θ
=cos²θ

√1-sin^2θ=|cosθ|=-cosθ