How would I solve this?
Find the rate of change of the distance between the origin and a moving point on the graph of y-sinx if dx/dt =2cm/sec when x= pi/2
Ok, this is what you're looking for:
Use the distance formula:
$\displaystyle s=\sqrt{(x-0)^2+(sin(x)-0)^2}=\sqrt{x^2+sin^2(x)}$
Now find the derivative with respect to x: $\displaystyle \frac{ds}{dx}$ and find it's value at the given point. Then just use the chain rule:
$\displaystyle \frac{ds}{dt}=\frac{ds}{dx}\frac{dx}{dt}$