1、cosπ/12*cos5π/12=cosπ/12*cos(π/2-π/12)=cosπ/12*sinπ/12=0.5sinπ/6=0.5*0.5=0.25;2.（cosπ/12－sinπ/12）×（cosπ/12＋sinπ/12）=cos^2π/12-sin^2π/12==conπ/6=0.5;3.因为 sin22°30′=√[(1-co...