Evaluate cos(-90 degrees )

Problem

cos(−90^∘)

Solution

1. Identify the property of the cosine function for negative angles. Cosine is an even function, which means cos(−θ)=cos(θ)

2. Apply the property to the given expression to rewrite it with a positive angle.

cos(−90^∘)=cos(90^∘)

3. Determine the value of the cosine function at 90^∘ using the unit circle or trigonometric tables. At 90^∘ the coordinates on the unit circle are (0,1)

4. Recall that the cosine of an angle corresponds to the xcoordinate of the point on the unit circle.

cos(90^∘)=0

Final Answer

cos(−90^∘)=0

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