(sin75度+cos75度)/(sin75度-cos75度)=?
题目
(sin75度+cos75度)/(sin75度-cos75度)=?
答案
sin75+cos75
=sin75+sin15
=2sin(75+15)/2cos(75-15)/2
=2sin45cos30
=√6/2
sin75-cos75
=sin75-sin15
=2cos(75+15)/2sin(75-15)/2
=2cos45sin30
=√2/2
(sin75度+cos75度)/(sin75度-cos75度)
=√6/2 / √2/2
=√3
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