# I forgot how to do the partial derivative of sin(x)cos(x), respect to x. Need Help!

1. Sep 10, 2008

### messedmonk

1. The problem statement, all variables and given/known data

partial derivative (d/dx) sin(x)cos(x)

2. Relevant equations

Partial Derivatives, product rule

3. The attempt at a solution

sin(2x) = 2 sin x cos x, therefore y=sin(2x)/2

so y'=cos(2x)*(2/2) = cos (2x)?

Is this correct?
Is there an easier way of directly finding the derivative without using substitution?

2. Sep 10, 2008

### rocomath

Re: I forgot how to do the partial derivative of sin(x)cos(x), respect to x. Need He

I don't see why you would be using partial differentiation with this problem? It is not a product of two variables?

No, that's the quickest method. Use the trig identity to avoid product rule.

Either way, GOOD JOB!!!

Last edited: Sep 10, 2008