Step-by-step explanation:
There are several ways we can do this.
x = cos t, y = sin t, t ≥ 0 traces the unit circle in a counterclockwise direction starting at (1, 0).
To change the direction, we can multiply one of these by -1. Then choose an initial value of t so that the starting point is (-1, 0).
x = -cos t, y = sin t, t ≥ 0
x = cos t, y = -sin t, t ≥ π
Or, we can change the direction by switching the equations.
x = sin t, y = cos t, t ≥ 3π/2
We can also multiply both by -1:
x = -sin t, y = -cos t, t ≥ π/2
Of these four examples, I would say the first is the simplest and most straightforward, but all of them achieve the same result.
