问题标题：
sin(-480度)cos570度+cos(-300度)sin(-1050)急
问题描述：
sin(-480度)cos570度+cos(-300度)sin(-1050)
急
洪菁回答：
sin(-480度)cos570度+cos(-300度)sin(-1050)
=-sin480°cos(360°+210°)+cos300°*(-sin1050°)
=-sin(360°+120°)cos210°-cos(360°-60°)sin(3*360°-30°)
=-sin120°cos(180°+30°)-cos60°(-sin30°)
=-sin(180°-60°)(-cos30°)+cos60°sin30°
=sin60°cos30°+cos60°sin30°
=sin(60°+30°)
=sin90°
=1
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