Find the Exact Value cos(-90 degrees )

Problem

cos(−90)

Solution

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

cos(−90)=cos(90)

2. Identify the coordinates on the unit circle at 90 The point corresponding to 90 (or π/2 radians) is (0,1)

(x,y)=(0,1)

3. Determine the cosine value by looking at the xcoordinate of the point on the unit circle.

cos(90)=0

Final Answer

cos(−90)=0

Want more problems? Check here!