求证:sin 2a/1+sin a+cos a=sin a+cos a-1急
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求证:sin2a/1+sina+cosa=sina+cosa-1急求证:sin2a/1+sina+cosa=sina+cosa-1急求证:sin2a/1+sina+cosa=sina+cosa-1急s
求证:sin 2a/1+sin a+cos a=sin a+cos a-1急
求证:sin 2a/1+sin a+cos a=sin a+cos a-1
急
求证:sin 2a/1+sin a+cos a=sin a+cos a-1急
sin 2a/1+sin a+cos a
=2sinacosa/(1+sina+cosa)
=(1+2sinacosa-1)/[(sina+cosa)+1]
=[(sin²a+2sinacosa+cos²a)-1]/[(sina+cosa)+1]
=[(sina+cosa)+1][(sina+cosa)-1]/[(sina+cosa)+1]
=(sina+cosa)-1
=sina+cosa-1
求证:sin 2a/1+sin a+cos a=sin a+cos a-1急
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