sin(2x)/2cosx(1+tanxtanx/2)
=[(2sinxcosx)/2cosx](1+tanxtanx/2)
=[(sinxcosx)/cosx](1+tanxtanx/2)
=sinx(1+tanxtanx/2)
=sinx[1+(sinx/cosx)*(1-cosx)/(sinx)]=sinx[1+(1-cosx)/cosx]
=sinx/cosx
=tanx