y=ln(tanx)/ln(sinx)
dy/dx = [lnsinx .d/dx(lntanx) - lntanx d/dx(lnsinx) ] /[ln(sinx)]^2
= [lnsinx .(1/tanx) (secx)^2 -lntanx .(1/sinx) cosx ] /[ln(sinx)]^2