Malorie's Holiday BLog #1

In this blog i'm looking back to the easiest stuff I learned. 7-4 reference angles.

To find a reference angle for sin and cos, you must follow the following:

Step 1: Figure out which quadrant the angle is in.
(if given an angle with pi, use pi as 180 and simplify)

Step 2: determine whether the function is positive or negative.

Step 3: subtract 180 from the angle measure until it is between 0 and 90 degrees.

Step 4: If the angle comes out to be 0, 30, 45, 60, or 90 degrees, use the trig chart to simplify. If not, then leave it as is or plug it in the calculator.

Example:
Find a reference angle for sin 6pi/5

sin (6x180)/5 = 1080/5 = 216

-sin216
this angle would be in the III quadrant because it is between 180 and 270. It would be negative because sin follows the y axsis and y is negative in this quadrant.

216-180 = 36
subtract from 180

your final answer would be -sin36 degrees.