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.