求值sin10度+sin50度-sin70度
问题描述：
求值sin10度+sin50度-sin70度
答
sin10°+sin50°-sin70°
=sin(20°+30°)+sin10°-sin70°
=√3/2 * sin20°+1/2 * cos20°-cos20°+sin10°
=√3/2*sin20°-1/2*cos20°+sin10°
=sin20°cos30°-sin30°cos20°+sin10°
=sin(20°-30°)+sin10°
=-sin10°+sin10°
=0
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