Question

Find the equation of tangents to the curve $y=\cos x,x\in \left[-2\pi ,2\pi \right]$ , which passes through $(0,1)$

Answer 1

The equation of curve $y=\cos x$

The slope of tangent is $\frac{dy}{dx}=\frac{d}{dx}\cos x\frac{dy}{dx}=-\sin x{\frac{dy}{dx}|}_{(0,1)}=-\sin 0=0$

it passes through $(0,1)$

$⟹y-1=0(x-0)y=1$

It is the equation of tangent