dl920
幼苗
共回答了19个问题采纳率:89.5% 举报
1.原式=(sina/cosa)(cosa-sina)+[sina+(sina/cosa)]/[(cos/sina)+(1/sina)]
=sina-(sin²a/cosa)+[sin²a+(sin²a/cosa)]/(cosa+1)
=sina-(sin²a/cosa)(cosa+1)/(cosa+1)+(sin²a/cosa)/(cosa+1)+sin²a/(cosa+1)
=sina+(sin²a/cosa)[1-(cosa+1)]/(cosa+1)+sin²a/(cosa+1)
=sin-sin²a/(cosa+1)+sin²a/(cosa+1)
=sina
2.原式=(1-cos²a)(sina/cosa)+(1-sin²a)(cosa/sina)+2sinacosa
=(sina/cosa)-sinacosa+(cosa/sina)-sinacosa+2sinacosa
=(sina/cosa)+(cosa/sina)
=(sin²a+cos²a)/sinacosa
=1/sinacosa
=2/2sinacosa
=2/sin2a
1年前
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