
sin200sin310+cos340cos50 谁给解一下
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sin200sin310+cos340cos50
=sin(180+20)sin(360-50)+cos(360-20)cos50
=-sin20sin(-50)+cos(-20)cos50
=sin20sin50+cos20cos50
=cos(50-20)
=cos30
=√3/2
=sin(180+20)sin(360-50)+cos(360-20)cos50
=-sin20sin(-50)+cos(-20)cos50
=sin20sin50+cos20cos50
=cos(50-20)
=cos30
=√3/2
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