计算:cosπ/15×cos2π/15×cos4π/15×cos8π/15
题目
计算:cosπ/15×cos2π/15×cos4π/15×cos8π/15
答案
cosπ/15×cos2π/15×cos4π/15×cos8π/15=(sinπ/15×cosπ/15×cos2π/15×cos4π/15×cos8π/15)/(sinπ/15)=(1/2sin2π/15×cos2π/15×cos4π/15×cos8π/15)/(sinπ/15)=(1/4sin4π/15×cos4π/15...
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