[tex] sin^{2} \alpha + cos^{2} \alpha = 1 \\ \\ or \\ cos \ \alpha = \sqrt{1- sin^{2} \alpha } \\ \\ [/tex]
The sin and cosine of any angle, α is positive in first quadrant 0-90,
sine is positive in 90-180, and the cosine in fourth quadrant 270-360.
Thus, these angles follow the pattern.
