Whats the derivative of sin^2(theta)?

[M. next]

but i need the derivative wrt time where theta depends on time

 

[Mark44]

but i need the derivative wrt time where theta depends on time

Use the chain rule.
$$\frac{d}{dt}sin^2(\theta) = \frac{d}{d\theta}sin^2(\theta)\cdot \frac{d\theta}{dt} = ? $$

 

[M. next]

then it is simply 2sin(theta)cos(theta)*(theta dot)

 

[Mark44]

Yes, that's it.