Question

已知sin(a+b)=2/3,sin(a-b)=1/5,则tan a/tan b=?

Answer 1

因为sin(a+b)=2/3,sin(a-b)=1/5,所以sinacosb=1/2[sin(a+b)+sin(a-b)]=13/30,所以sinbcosa=2/3-13/30=7/30,所以tana/tanb=sinacosb/(sinbcosa)=13/7