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  1. 9-89. Evaluate each of the following trig expressions without using a calculator. Homework Help ✎

    1. sin(180º)

    2. sin(360º)

    3. sin(–90º)

    4. sin(510º)

    5. cos(90º)

    6. tan(–90º)

Every point on the unit circle is defined as (cos (θ), sin (θ)).
Where is 180° on the unit circle?
Where is the y-value at that point?


See part (a).

When an angle is negative, it opens clockwise from 0° on the unit circle.

Find an equivalent angle between 0° and 360° by subtracting 510 − 360. Notice that the reference
triangle is a 30°-60°-90° triangle. Find the sin (30°).


What is the x-value in this location?