Find the derivative of sinxcosx using first principles Share with your friends Share 10 Ankush Jain answered this Let f (x) = sin x cos x. Accordingly, from the first principle, 10 View Full Answer Mani Maran answered this use sin2x formula first i.e multiply and divide by 2.i found out the solution but word limit problem 1 Mani Maran answered this 2sin(x+h) cos(x+h) - 2sinx cosx / 2h 7 Mani Maran answered this sin(2x+2h) - sin2x /2h 4 Mani Maran answered this now sin a- sinb formula the ans is cos2x 10 Raghavendra Kulkarni answered this d/dx(sinx.cosx)=sinx.d/dx(cosx) + cosx.d/dx(sinx)=sinx(-sinx) + cosx(cosx)=cos2x 10