化简(2cosa^2-1)/(2tan(π/4-a)*sin(π/4+a)^2)
问题描述:
化简(2cosa^2-1)/(2tan(π/4-a)*sin(π/4+a)^2)
答
sin(π/4+a)=cos[π/2-(π/4+a)]=cos(π/4-a) sin(π/4-a)·sin(π/4+a)=(sinπ/4cosa-sinacosπ/4)(sinπ/4cosa+sinacosπ/4)=(cosa·√2/2-sina·√2/2)(cosa·√2/2+sina·√2/2)=cos²a·1/2-sin²a·1/...