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mathdad

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1. sin 210°

A. We are told to graph sin 210°. We are in Quadrant 3.

B. Find the reference angle R.

R = 270° - 210°

R = 60°

C. Evaluate sin R.

sin 60° = -sqrt{3}/2

Book's answer is -1/2.

2. sin (-210°)

A. We are told to graph sin (-210°).

We are in Quadrant 2.

B. Find the reference angle R.

R = -270° - (-210°)

R = -270° + 210°

R = -60

C. Evaluate sin R

sin (-60°) = sqrt{3}/2

Book's answer is 1/2.