We draw a table of values:

t 0 π/4 π/2 3π/4 π 5π/4 3π/2 7π/4 2π
x 0.7 0 -0.7 -1 -0.7 0 0.7 1 0.7
y 0 1 0 -1 0 1 0 -1 0
Pt
no.
1 2 3 4 5 6 7 8 9

The sketch is:

math expression

This curve is part of a parabola.

Of course, it would have been better to start our values from t = 3π/4 (Point 4) and only use Points 4, 5, 6, 7, and 8. But you don't know that until you have drawn it.