化简:(xcosa+ysina) + (ycosa-xsina)=_______?

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化简:(xcosa+ysina)+(ycosa-xsina)=_______?化简:(xcosa+ysina)+(ycosa-xsina)=_______?化简:(xcosa+ysina)+(ycos

化简:(xcosa+ysina) + (ycosa-xsina)=_______?
化简:(xcosa+ysina) + (ycosa-xsina)=_______?

化简:(xcosa+ysina) + (ycosa-xsina)=_______?
答案为x^2+y^2

=x+y (xcosa+ysina) + (ycosa-xsina)=xcosa+2xycosasina+ysina+ycosa-2yxcosasina+xsina=x(cosa+sina)+y(sina+cosa)=x+y