Answer:
see below
Step-by-step explanation:
A picture can explain a lot. The coordinates are shown in the attachment.
Positive angles are measured counterclockwise (CCW). Negative angles are measured clockwise. So, -3π/4 is the same as +5π/4, since a circle is 2π = 8π/4.
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It can be useful to memorize this chart, or keep one like it for handy reference.
