Reference Angles

This week in advanced math we covered most of chapter seven. We learned how to convert degrees to radians and vice versa. In seven-two we learned we learned some important formulas that we will need. We also learned how to read word problems and pull certain parts of the formula out of the word problem. Next we learned about sin, cos, the unit circle , and pythagorean triples. Cos always has to do with x and sin always has to do with y. We went on to learn the Trig chart, tan, cot, sec, and csc. But what i found easiest to do for me was finding reference angles.

To find a reference angle you must first find the quadrant that the angle is in. Next you must determine if the trig function is positive or negative. Then you subtract 180 degrees from the angle until the absolute value of theta is between 0 and 90 degrees. Last of all if the angle you end up with is a trig chart angle you plug in the trig chart number. If not you either leave it as it is or plug it into your calculator.

Ex. Find the reference angle for cos 525 degrees

First you find which quadrant 525 degrees is in on the graph to determine if cos is positive or negative.

525 degrees is located in quadrant 2 which has a x value of -1, which means cos(x/r) equals -1/1, therefore cosine is negative.

Next continue to subtract 525 by 180 until you get in between 0 and 90 degrees.

525-180= 345-180=165-180=-15

The absolute value of -15 =15

Therefore -cos=15 degrees