问题标题：
又一道数学题化简:cos平方(a+15度）+sin方(a-15度）+sin(a+180度)*cos(a-180度）
问题描述：
又一道数学题
化简:cos平方(a+15度）+sin方(a-15度）+sin(a+180度)*cos(a-180度）
童建平回答：
cos^2(a+15)+sin^2(a-15)+sin(a+180)cos(a-180)
=cos^2(a+15)+sin^2(a+15)-sin^2(a+15)+sin^2(a-15)+sinacosa
=1+[sin^2(a-15)-sin^2(a+15)]+sinacosa
=1+[sin(a-15)+sin(a+15)][sin(a-15)-sin(a+15)]+sinacosa
=1+[2sinacos15]*[2cosa*sin(-15)]+sinacosa
=1-sin2a*sin30+(1/2)*sin2a
=1-(1/2)*sin2a+(1/2)*sin2a
=1
楼上和我一样?
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