(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2/2+1/4.
(cosπ/8+sinπ/8)（cos^3π/8-sin^3π/8）.
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