First, put Sina =

3/5sinC of the original formula sinAcosB-sinBcosA

Sin (AB)= 3/5sin(A+B)

Then use cosAsinB to divide the two sides.

Regarding the point, we can get sinAcosB/cosAsinB = 4.

Because tanAcotB = sinAcosB/cosAsinB

So, the result is 4

Professional knowledge of the industry Qin, play insufficient. What I did was thought, but it was destroyed.