求值：sin10°sin50°sin70°sin8 - 知识问答

求值：sin10°sin50°sin70°sin80°

1个回答

题目错了吧sin80应该是sin30
sin10sin30sin50sin70
=cos10sin10sin30sin50sin70/cos10
=1/2sin20sin70sin30sin50/cos10
=1/4sin40sin50sin30/cos10
=1/8sin80sin30/cos10
=1/8cos10sin30/cos10
=1/8sin30
=1/8*1/2
=1/16

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