# Math Help - Differentiation- Product Rule

1. ## Differentiation- Product Rule

Find the gradients of the curve $y=x\sqrt{4-x^2}$ at the points where it crosses the straight line $y=x$

2. I am becoming concerned about people posting problems without showing even an attempt at the problem. Write $y= x\sqrt{4- x^2}= x(4- x^2)^{1/2}$ and use the product rule, that you refer to and the chain rule on $(4- x^2)^{1/2}$. Since the problem asks for the derivate where the curve crosses y= x, you will need to solve $y= x= x\sqrt{4- x^2}$ to determine the x values.

3. Sorry about that, I have already attempted the question five times and have finally found the problem. Thanks. The problem was I didn't + - for square root of 3