# Math Help - Rectangular coordinate

1. ## Rectangular coordinate

How would I find the rectangular coordinate of the point P on the unit circle that corresponds to t=-[pi]/2?

2. Originally Posted by gretchen
How would I find the rectangular coordinate of the point P on the unit circle that corresponds to t=-[pi]/2?
Hello, Gretchen,

the point P has the coordinates P(r*cos(t), r*sin(t)). Since r = 1 the point P is P(0, -1)

EB

3. Originally Posted by gretchen
How would I find the rectangular coordinate of the point P on the unit circle that corresponds to t=-[pi]/2?
x = r*cos(theta)
y = r*sin(theta)

The point is (1, -(pi)/2), so we have:
x = 1*cos(-(pi)/2) = 1*cos((pi)/2) = 1*0 = 0
y = 1*sin(-(pi)/2) = -1*sin((pi)/2) = -1*1 = -1

So the point (1, -(pi)/2) corresponds to the rectangular coordinate point (0, -1).

-Dan