OpenStax, Algebra and Trigonometry 2e §7.3 Unit Circle · Example 4 · Trigonometry · Unit circle

Using Reference Angles to Find Sine and Cosine

ⓐ Using a reference angle, find the exact value of $cos (150°)$ and $sin (150°) .$
ⓑ Using the reference angle, find $cos \frac{5 π}{4}$ and $s in \frac{5 π}{4} .$

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OpenStax, Algebra and Trigonometry 2e · §7.3 Unit Circle · Example 4

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