Hello, can someone please help me to set this problem up. Let theta(in radians) be an acute angle in a rt triangle, and let x and y respectively be the lengths of the sides adj and opp to theta. Suppose x and y vary with time.

At a certain instant, x =2 units and is increasing at 1 unit/s, while y = 2 units and is decreasing at 1/4 unit/s. How fast is theta chaning at that instant?

I know the answer is d0/dt = cos^0/x^O(x(dy/dt) - y(dx/dt) where I am representing 0 as theta.

Thanks,

Pantera