Pre-Calculus - Evaluating the cosine of an angle using the sum formula cos(11π/12)

The video tutorial explains how to evaluate the cosine of 11π/12 by expressing it as the sum of two angles, 3π/4 and π/6, which are found on the unit circle. The instructor demonstrates the use of the cosine addition formula, evaluates the cosine and sine of the individual angles, and simplifies the result. The importance of understanding the unit circle is emphasized for solving such problems.

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