题目
cos20°sin40°+sin20°sin50°等于( )
A.
A.
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提问时间:2021-01-20
答案
cos20°sin40°+sin20°sin50°
=cos20°cos50°+sin20°sin50°
=cos(50°-20°)
=cos30°
=
=cos20°cos50°+sin20°sin50°
=cos(50°-20°)
=cos30°
=
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