Respuesta :

3π/4 angle is in the second quadrant, so cos (3π/4) is going to be negative.

Reference angle of 3π/4 is (π - 3π/4) = π/4

cos(π/4) = √2/2

cos (3π/4) = - √2/2

Answer is C.

Answer:

Answer C: negative square root of 2 over 2

Step-by-step explanation:

The reason being that the reference is pi over 4.