已知tana=2/5,tanb=3/7求tan(a+b),tan(a-b).
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![已知tana=2/5,tanb=3/7求tan(a+b),tan(a-b).](/uploads/image/z/6865092-36-2.jpg?t=%E5%B7%B2%E7%9F%A5tana%3D2%2F5%2Ctanb%3D3%2F7%E6%B1%82tan%28a%2Bb%29%2Ctan%EF%BC%88a-b%EF%BC%89.)
已知tana=2/5,tanb=3/7求tan(a+b),tan(a-b).
已知tana=2/5,tanb=3/7求tan(a+b),tan(a-b).
已知tana=2/5,tanb=3/7求tan(a+b),tan(a-b).
tan(a+b)
=(tana+tanb)/(1-tanatanb)
=(2/5+3/7)/(1-2/5*3/7)
=(14/35+15/35)/(1-6/35)
=(29/35)/(29/35)
=1
tan(a-b)
=(tana-tanb)/(1-tanatanb)
=(2/5-3/7)/(1+2/5*3/7)
=(14/35-15/35)/(1+6/35)
=(-1/35)/(41/35)
=-1/41