Originally Posted by

**bigwave** basically I don't understand the suggestion on how this was set up

Let $\displaystyle \theta$ (in radians) be an angle in a right triangle, and let x and y, respectively, be the lengths of the sides adjacent to and opposite $\displaystyle \theta$ Suppose that x and y vary with time.

(a) How are $\displaystyle \frac{d\theta}{dt}$ , $\displaystyle \frac{dx}{dt}$ and $\displaystyle \frac{dy}{dt}$ Related

the book says that

$\displaystyle \frac{d\theta}{dt}=\frac{cos^2\theta}{x^2}\left( x \frac{dy}{dt}-y\frac{dr}{dt}\right)$

thanks for help

actually I don't know where the $\displaystyle \frac{cos^2\theta}{x^2}$ comes from I assume the hypotenuse is a constant