Write the equation of the normal to the curve

Given that $y=\cos x$

On differentiating both the sides w.r.t. $x$

$\frac{d y}{d x}=-\sin x$

Now,

Slope of tangent at $(0,1)=0$

Equation of normal:

$\left(\mathrm{y}-\mathrm{y}_{1}\right)=\frac{-1}{\text { Slope of tangent }}\left(\mathrm{x}-\mathrm{x}_{1}\right)$

$\Rightarrow(\mathrm{y}-1)=\frac{-1}{0}(\mathrm{x}-0)$

$\Rightarrow \mathrm{x}=0$