cos^2 80度 sin^2 50度-sin190cos320=
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cos^2 80度 sin^2 50度-sin190cos320=
cos^2(80)+sin^2(50)-sin190cos320
=sin^2(10)+cos^2(40)+sin10cos(360-40)
=sin^2(10)+cos^2(40)+sin10cos40
=(sin10+cos40)^2-sin10cos40
=(sin10+sin50)^2-sin10sin50
=(2sin30cos20)^2+(1/2)(cos60-cos40)
=cos^2(20)+1/4-cos^2(20)+1/2
=3/4
=sin^2(10)+cos^2(40)+sin10cos(360-40)
=sin^2(10)+cos^2(40)+sin10cos40
=(sin10+cos40)^2-sin10cos40
=(sin10+sin50)^2-sin10sin50
=(2sin30cos20)^2+(1/2)(cos60-cos40)
=cos^2(20)+1/4-cos^2(20)+1/2
=3/4
cos^2 80度 sin^2 50度-sin190cos320=
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