Could someone check my solution? Finding the equation of the tangent line to y=cos(2x) at x=pi/4

Find the equation of the tangent line to y=cos(2x) at x=pi/4

$f(x) = cos(2x) = cos(2\times \frac{pi}{4} ) = 0$

So the value of y is zero. Which gives us the point $(\frac{pi}{4}, 0)$

So to find the slope, we use the derivative:

$f'(x) = -2sin(2x)$

$f'(\frac{pi}{4}) = -2$

And get that the slope = -2.

Therefore, the solution is:

$y = -2(x - \frac{pi}{4})$