$\"\"$

The function is $\"f\\left$ .

Differentiate on each side with respect to $\"x\"$ .

$\"\\\\f\'\\left$

Derivative of the sine function: $\"\\frac{d}{dx}\\sin$ .

$\"\\\\f\'\\left$ .

Slope of the tangent is derivative of the function.

$\"m=f\'\\left$ .

The function has horizontal tangent where slope of the tangent is zero.

Thus, $\"\\\\1+2\\cos$

$\"\\\\\\cos$ .

General solution of $\"x\"$ is $\"x=(2n+1)\\pi$ .

$\"\"$

$\"x=(2n+1)\\pi$ .