Evaluate f ′ ( x ) f^{\prime}\left(x\right) at x = π 4 x=\frac{\pi}{4} if f ( x ) = cos ⁡ x f\left(x\right)=\cos x .

Derivatives of Trig Functions

3. Techniques of Differentiation / Derivatives of Trig Functions / Problem 1

Problem 1

Evaluate $f^{'} (x)$ at $x = \frac{π}{4}$ if $f (x) = \cos x$ .

$\frac{1}{2}$

$\frac{\sqrt{3}}{2}$

$\frac{\sqrt{2}}{2}$

$- \frac{\sqrt{2}}{2}$