Find the Exact Value cos(-pi/6)

Problem

cos(−π/6)

Solution

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

cos(−π/6)=cos(π/6)

2. Identify the reference angle on the unit circle. The angle π/6 corresponds to 30

π/6=30

3. Determine the exact value using the coordinates of the unit circle or a special right triangle (30−60−90.

cos(π/6)=√(,3)/2

Final Answer

cos(−π/6)=√(,3)/2

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