Find the Exact Value cos(-270 degrees )

Problem

cos(−270)

Solution

1. Identify the angle in standard position by adding 360 to find a coterminal angle.

−270+360=90

2. Determine the coordinates on the unit circle for the angle 90

(x,y)=(0,1)

3. Apply the definition of the cosine function on the unit circle, where cos(θ)=x

cos(90)=0

4. Conclude that since the angles are coterminal, their cosine values are identical.

cos(−270)=cos(90)=0

Final Answer

cos(−270)=0

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