College Algebra & Trigonometry, 2018a

9.1. TRIGONOMETRIC FUNCTIONS OF NON-ACUTE ANGLES 389
Example 1 Quadrant II
In Quadrant II, x-coordinates are negative and y-coordinates are positive. This
means that cos θ0. The values for this process are given below:
sin 52 ◦ ≈ 0.7880 sin 128 ◦ ≈ 0.7880
cos 52 ◦ ≈ 0.6157
cos 128 ◦ ≈−0.6157
tan 52 ◦ ≈ 1.280
tan 128 ◦ ≈−1.280
Example 2 Quadrant III
In Quadrant III, x-coordinates are negative and y-coordinates are also negative.
This means that cos θ0
tan θ>0
cos θ