Find the Reference Angle cos(105)

Problem

cos(105)

Solution

1. Identify the quadrant in which the given angle θ=105 lies. Since 90<105<180 the angle is in Quadrant II.

2. Apply the formula for the reference angle θ′ in Quadrant II. The reference angle is the acute angle formed by the terminal side and the x-axis.

3. Calculate the value using the formula θ′=180−θ

θ′=180−105

θ′=75

Final Answer

Reference Angle of *105=75

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