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## Precalculus

### Unit 2: Lesson 2

Trigonometric identities on the unit circle

# Trig identities from reflections and rotations

## Problem

On the following unit circle, theta is in radians.
A unit circle with an angle from the positive x-axis to a ray labeled theta. The point where the ray intersects the circle is labeled negative 0.42, 0.91 and is in the second quadrant.
Without a calculator, evaluate the following expressions to the nearest hundredth.
ExpressionValue
cosine, left parenthesis, pi, minus, theta, right parenthesis
cosine, left parenthesis, 2, pi, plus, theta, right parenthesis
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