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问题: 化简不同角的三角函数题

Sin2A+sin2B-sin2A *sin2B+cos2A*cos2B (注"2"代表平方)

解答:

Sin^A+sin^B-sin^A *sin^B+cos^A*cos^B= (注"^"代表平方)
Sin^A+sin^B(1-sin^A )+cos^A*cos^B=
Sin^A+sin^B*cos^A +cos^A*cos^B=
Sin^A+cos^A *(sin^B+cos^B)=
Sin^A+cos^A *(sin^B+cos^B)=
Sin^A+cos^A *1=
Sin^A+cos^A =1