Take a look at the attached picture of the unit circle.
If you have negative radians, you would go around the circle counterclockwise starting from 0. Remember that 1π is a semicircle. Go counterclockwise 1π to get to 180° or (-1,0).
Now you just need to go counterclockwise 3π/4 more, since 7π/4 is 3π/4 more than π. 3/4 of π would just be 3/4 of a semicircle. (Try to imagine that in your head. It looks like 3 slices of a pizza that was cut into 8 slices.) The second picture shows you moving 3π/4 from π on the unit circle, which would put you at 45° or π/4.
At π/4, the coordinates are [tex] (\frac{ \sqrt{2} }{2} , \frac{ \sqrt{2} }{2} )[/tex].
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Answer: [tex] (\frac{ \sqrt{2} }{2} , \frac{ \sqrt{2} }{2} )[/tex]
