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Home > PC3 > Chapter 4 > Lesson 4.2.1 > Problem 4-61

4-61.

Study the diagram of the unit circle at right.  

If is the origin, . Use the Pythagorean Theorem to determine .

This angle is in Quadrant III. Should and each be considered positive or negative?

  1. Evaluate sin(θ).

  2. Evaluate cos(θ).

  3. If α is another angle with the same sine as θ, but a different cosine, in what quadrant is α?

    For θ, sine and cosine are both negative.
    In what quadrant is sine negative and cosine positive?

  4. If β is another angle with the same cosine as θ, but a different sine, in what quadrant is β?

    For θ, sine and cosine are both negative.
    In what quadrant is sine positive and cosine negative?