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问题: 高1数学B组6题

sinb=msin(2a+b)且m≠1 , a≠k派/2,a+b≠派/2+k派(k∈Z)
求证tan(a+b)=[(1+m)/(1-m)]tana

解答:

sinb=msin(2a+b)
==> sin[(a+b)-a] = m*sin[(a+b)+a]
==> sin(a+b)cosa - cos(a+b)sina = m*[sin(a+b)cosa + cos(a+b)sina]
==> tg(a+b) - tga = m*[tg(a+b) + tga]
==> tg(a+b) = [(1+m)/(1-m)]tga