Question

Determine all x in [−π/2, π/2] at which the graph has horizontal tangents

F'(x) = 4cos^3(x)/(sin^2(x)+1)^2

Answer 1

I found the derivative and i should set the numerator equals to zero but im getting stuck for some reason

Answer 2

Yeah, let the numerator equal 0.
Show me your derivative.

Answer 3

thats my derivative

Answer 4

I didn't write the F(x) i wrote F'(x)

Answer 5

Yeah, let the numerator equal 0.

Answer 6

im having trouble solving for it im getting x = pi n -pi/2 but ti says is wrong