Find the Exact Value cos(2*(3pi)/4)

$\cos (2 \cdot \frac{3 π}{4})$

Cancel the common factor of $2$ .

Factor $2$ out of $4$ .

$\cos (2 \cdot \frac{3 π}{2 (2)})$

Cancel the common factor.

$\cos (2 \cdot \frac{3 π}{2 \cdot 2})$

Rewrite the expression.

$\cos (\frac{3 π}{2})$

Apply the reference angle by finding the angle with equivalent trig values in the first quadrant.

$\cos (\frac{π}{2})$

The exact value of $\cos (\frac{π}{2})$ is $0$ .

$0$