Find the exact values of cos 3 pi/4 radians sin 3 pi/4 radians !

In degrees: 3π/4 radians = 135°
Angle of x=135° is in the 2nd Quadrant and has negative cos x values and positive sin x values.
cos 135° = cos ( 90° + 45°)= - sin 45° =
sin 135° = sin ( 90° + 45° ) = cos 45° =. You can also see the graph in the attachment.