(sinA+sinB)/(cos A +cos B) =tan (A+B)/2 怎么证明?
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(sinA+sinB)/(cos A +cos B) =tan (A+B)/2 怎么证明?
![(sinA+sinB)/(cos A +cos B) =tan (A+B)/2 怎么证明?](/uploads/image/z/1163687-23-7.jpg?t=%28sinA%2BsinB%29%2F%28cos+A+%2Bcos+B%29+%3Dtan+%28A%2BB%29%2F2+%E6%80%8E%E4%B9%88%E8%AF%81%E6%98%8E%3F)
(sinA+sinB)/(cos A +cos B)
=2sin(A+B)/2*cos(A-B)/cos2/cos(A+B)/2*cosA-B)/2
=sin(A+B)/2/cos(A+B)/2
=tan (A+B)/2
用和差化积公式
=2sin(A+B)/2*cos(A-B)/cos2/cos(A+B)/2*cosA-B)/2
=sin(A+B)/2/cos(A+B)/2
=tan (A+B)/2
用和差化积公式
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