Find the Value Using the Unit Circle cos(-1.9967)

Problem

cos(−1.9967)

Solution

1. Identify the angle and its units. The angle is −1.9967 radians. Since there is no degree symbol, we assume the value is in radians.

2. Determine the quadrant of the angle. Since π≈3.14159 and π/2≈1.5708 the angle −1.9967 lies between −π/2 and −π This corresponds to the third quadrant in the unit circle.

3. Apply the even-odd property of the cosine function. The cosine function is even, meaning cos(−θ)=cos(θ)

4. Calculate the value using a calculator or reference table. Ensure the calculator is set to radian mode.

cos(−1.9967)=cos(1.9967)

cos(1.9967)≈−0.4121

Final Answer

cos(−1.9967)=−0.4121

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