Question

Using implicit differentiation to find the two points with a horizontal tangent line. Two points for which dy/dx = 0. Using the equation y^2 = x^2 + cos x.

Answer 1

\[2yy'=2x-\sin(x)\] is a start

Answer 2

Then I would get y' = [2x - sin(x)] / 2y

When y'=0,

0 = [2x - sin(x)] / 2y
2x - sin(x) = 0
x = 0 (if could take out the x)

So my first point will be 0 (x,y). Anyone can verify?