OpenStax, Precalculus 2e §7.4 Sum-to-Product and Product-to-Sum Formulas · Example 5 · Trigonometry · Compound & multiple angles

Evaluating Using the Sum-to-Product Formula

Evaluate $cos (1 5^{\circ}) - cos (7 5^{\circ}) .$

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OpenStax, Precalculus 2e · §7.4 Sum-to-Product and Product-to-Sum Formulas · Example 5

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