Use the unit circle to complete Exercises (see Example 5).

Find cos 0°.

Data from Example 5

(a) Use the unit circle to find cos 90° and sin 90°. A 90° angle, when placed in standard position, intersects the unit circle at the point (0, 1). Therefore, cos 90° = x = 0 and sin 90° = y = 1.

(b) Find cosθ and csc θ if the terminal side of θ (in standard position) intersects the unit circle at the point (0.6, 0.8). We know that cosθ = x = 0.6. Since sinθ = y = 0.8, cscθ is the reciprocal of 0.8.

Thus,

csc 0 || = -13 || 0.8 0 || El