If $x=2 \cos t-\cos 2 t$ and $y=2 \sin t-\sin 2 t$, then at $t=\frac{\pi}{2}, \frac{d y}{d x}=$

Question

Professor PC Thomas Classes · Answer

Using parametric differentiation $\frac{dy}{dx} = \frac{dy/dt}{dx/dt}$, evaluated precisely at $t = \pi/2$ yields $-1$.