d
--((log(cos(2*t)), y))
dy
$$\frac{\partial}{\partial y} \left( \log{\left(\cos{\left(2 t \right)} \right)}, \ y\right)$$
2
d
---((log(cos(2*t)), y))
2
dy
$$\frac{\partial^{2}}{\partial y^{2}} \left( \log{\left(\cos{\left(2 t \right)} \right)}, \ y\right)$$
3
d
---((log(cos(2*t)), y))
3
dy
$$\frac{\partial^{3}}{\partial y^{3}} \left( \log{\left(\cos{\left(2 t \right)} \right)}, \ y\right)$$