Question

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

Answer 1

sin(a+b)=sinacosb+cosasinb =1/5 sin(a-b)=sinacosb-cosasinb=1/3

所以sinacosb=4/15 cosasinb=-1/15

(sinacosb)/(cosasinb)=4/15/（-1/15）=-4