Find the Exact Value cos(-pi/3)

Problem

cos(−π/3)

Solution

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

cos(−π/3)=cos(π/3)

2. Identify the reference angle in the first quadrant. The angle π/3 is a standard angle equivalent to 60

π/3=60

3. Determine the exact value using the unit circle or a special right triangle (30−60−90. The cosine of π/3 is 1/2

cos(π/3)=1/2

Final Answer

cos(−π/3)=1/2

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