sinπ/12cos5π/12等于
问题描述：
sinπ/12cos5π/12等于
答
sinπ/12cos5π/12
=sinπ/12sin(π/2-5π/12)
=(sinπ/12)^2
=[1-cos(2*π/12)]/2
=(1-cosπ/6)/2
=(2-√3)/4
答
积化和差公式：
sinAcosB=[sin(A+B)+sin(A-B)]/2
sinπ/12cos5π/12=[sinπ/2+sin(-π/3)]/2=(1-√3/2）/2=1/2-√3/4