A point (-0.8, 0.6) will be a point on the unit circle in the second quadrant. Since it is a unit circle, its radius is 1, and we have
sin(α) = y = 0.6
cos(α) = x = -0.8
tan(α) = y/x = 0.6/-0.8 = -0.75
The angle is α = arccos(-0.8) ≈ 143.13°
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For the unit circle, the trig values are always the coordinates or their ratio as shown above, regardless of quadrant.
