令a=x+y
b=x-y 则x=(a+b)/2,y=(a-b)/2
sina+sinb=sin(x+y)+sin(x-y)
=sinxcosy+sinycosx+sinxcosy-sinycosx
=2sinxcosy
将x=(a+b)/2,y=(a-b)/2代入
得sina+sinb=2[sin(a+b)/2][cos(a-b)/2]
sina+sinb=2sin((a+b)/2)cos((a-b)/2的推导过程
sina+sinb=2sin((a+b)/2)cos((a-b)/2的推导过程
数学人气:284 ℃时间:2019-10-19 12:57:31
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