Question

Find all points on the curve y = cos x, 0 ≤ x ≤ 2π, where the tangent line is parallel to the line y = -x.

Answer 1

90⁰

Explanation:

y=cosx

y'= -sinx

eqñ of tangent is y=-x

slope of tangent =-1

we know...

slope of tangent = y' or derivative of y

-sin x = -1

sin x= 1

x = 90⁰