Show that the point P is on the unit circle.

Solution:

We need to show that this point satisfies the equation of the unit circle, that is, x²_+_y²_=_1.

Therefore P is on the unit circle.

Example 2:

The point P is on the unit circle in quadrant IV. Find its y-coordinate.

Solution:

Since the point is on the unit circle, we have:

y² = 1 - 3/4 = 1/4
y = 1/2
Since the point is in quadrant IV, its y-coordinate must be negative, so y.=.-1/2.