Pre-Calculus - How to Evaluate Using the Double Angle Formula for Cosine

The video tutorial explains how to find the cosine of a double angle given the sine of an angle. It begins by introducing the problem and identifying the need to find the cosine of 2U. The instructor then discusses the selection of the appropriate formula, which is 1 - 2 sine^2(U), and explains why this formula is suitable for the problem. The tutorial proceeds with applying the formula by substituting the given sine value and performing the necessary calculations to arrive at the final result, which is -7/25.

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