The complex number is :
[tex]z=2 \ cis ( \frac{7 \pi }{8} )=2(\cos\frac{7 \pi }{8} +i \sin \frac{7 \pi }{8})[/tex].
Writing this point in the real x-y axis plane, we have:
[tex](x, y)=(2\cos\frac{7 \pi }{8} , 2 \sin \frac{7 \pi }{8})[/tex].
[tex]\frac{7 \pi }{8}[/tex] radians = (7/8)*180°=157.5°. We can find that:
cos(157.5°)=-0.924, so 2cos(157.5°)=-1.85
sin(157.5°)=0.383, so 2sin(157.5°)=0.77.
Answer: (-1.85, 0.77)
