The Missing Intercept

I posted this puzzle some time ago,

but no one provided a satisfactory answer.

Given: .

We have the parametric equations of a unit circle.

Verification

Square: .

Add [1] and [2]: .

Hence, a unit circle: .

To find the -intercepts, let

Hence, the -intercepts are: .

To find the -intercepts, let

Hence, the -intercept is: . ?

Where is the other -intercept?