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° =[tex]- \frac{ \sqrt{2} }{2} [/tex]
sin 135° = sin ( 90° + 45° ) = cos 45° =[tex] \frac{ \sqrt{2} }{2} [/tex]. You can also see the graph in the attachment.
