(cosπ/8+sinπ/8)(cos^3π/8-sin^3π/8).
问题描述:
(cosπ/8+sinπ/8)(cos^3π/8-sin^3π/8).
答
(cosπ/8+sinπ/8)(cos^3π/8-sin^3π/8)=(cosπ/8+sinπ/8)(cosπ/8-sinπ/8)(cos^2π/8+cosπ/8*sinπ/8+sin^2π/8)=(cos^2π/8-sin^2π/8)(1+0.5sinπ/4)=cosπ/4(1+0.5sinπ/4)=根下2/2(1+根下2/4)=根下...