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The Complete Idiot's Guide to Trigonometry by Izolda Fotiyeva, Dmitriy Fotiyev

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Evaluating Trigonometric Functions

Equipped with the knowledge on reference angles, you can apply it now to find trigonometric functions of different angles.

When asked to find trigonometric functions for an angle, you have to run some simple tests to identify the best strategy to find the answer the quickest way.

First, make sure that the angle of interest is not one of the special angles you’ve seen so many times. If it is, then you should know the answer right away.

The following problems illustrate how you should handle all other angles.

Sample Problem 1

Find the sine, cosine, and tangent for an angle of 225º.

Step 1: Identify the quadrant. This angle is between 180º and 270º, so the terminal side is in the third quadrant.

Step 2: Perform ...

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