Review of 7-4

This weekend I am going to review with you all the information that we learned in chapter 7, section 4. In this section we learned how to find reference angles of trig functions. Reference angles must be between 0 and 90 degrees. The reason for this is so that you can find the exact value by using the trig chart, the unit circle, or a calculator. There are a few steps in the process of finding a reference angle of a trig function.

Steps:
1. First of all you have to find the quadrant that the angle is in and sketch it.
2. Then you must use the unit circle to determine whether the angle is positive or negative.
3. Finally, you have to subtract either 360 degrees or 180 degrees until the absolute value of theta is between 0 and 90 degrees.
4. If the problem asks for the exact value, then you would use the trig chart, the unit circle, or a calculator to find it.

Example: Find the exact value of sin 210 degrees
• Sin 210 degrees is in quadrant 3
• Sin is negative in quadrant 3
• 210-180=30
• -sin 30 degrees = ½

-Braxton-