若θ为锐角,且sin(θ-60)=5/13,则sinθ=
问题描述:
若θ为锐角,且sin(θ-60)=5/13,则sinθ=
答
sin(θ-60)=5/13,θ是锐角,故可求得
cos(θ-60)=12/13
sinθ=sin[(θ-60)+60]
=sin(θ-60)cos60+cos(θ-60)sin60
=(12√3+5)/20