Evaluate cos(150 degrees )

Problem

cos(150)

Solution

1. Identify the reference angle by finding the distance from the angle to the nearest x-axis (180.

(θ_ref)=180−150=30

2. Determine the quadrant of the angle 150 which lies in Quadrant II.

3. Determine the sign of the cosine function in Quadrant II, where cosine values are negative.

cos(150)=−cos(30)

4. Substitute the known exact value for cos(30) which is √(,3)/2

cos(150)=−√(,3)/2

Final Answer

cos(150)=−√(,3)/2

Want more problems? Check here!