Find the Exact Value cos(-pi)

Problem

cos(−π)

Solution

1. Identify the angle within the unit circle. The angle is −π radians.

2. Apply the even-odd identity for the cosine function, which states that cos(−θ)=cos(θ)

3. Substitute the value into the identity to get cos(−π)=cos(π)

4. Evaluate the cosine of π using the unit circle. At π radians (180, the coordinates are (−1,0)

5. Determine the x-coordinate, which represents the cosine value at that angle.

Final Answer

cos(−π)=−1

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