Find the Exact Value cos(390)

Problem

cos(390)

Solution

1. Identify the angle as being greater than 360 and find its coterminal equivalent within the range [0,360)

2. Subtract 360 from the given angle to find the coterminal angle.

θ=390−360

θ=30

3. Apply the property that trigonometric functions of coterminal angles are equal.

cos(390)=cos(30)

4. Evaluate the cosine of 30 using the unit circle or special right triangles.

cos(30)=√(,3)/2

Final Answer

cos(390)=√(,3)/2

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