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Using Reference Angles to Find Sine and Cosine

Avg difficulty 2.5
  1. ⓐ Using a reference angle, find the exact value of cos(150°) \cos \left(150°\right) and sin(150°). \text{sin} \left(150°\right) .
  2. ⓑ Using the reference angle, find cos 5π 4 \cos \frac{5 \pi}{4} and sin 5π 4 . \sin \frac{5 \pi}{4} .

OpenStax Algebra and Trigonometry 2e, 7.3 Unit Circle, exercise 11

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Adapted from College Algebra © 2021 Rice University. Licensed under CC BY 4.0. Sources: College Algebra 2e, Algebra and Trigonometry 2e, Precalculus 2e, College Algebra with Corequisite Support 2e. Imported at revision 4922e46.