Tori's Holiday Blog #1

4 down, 3 to go!



To find a reference angle for sin and cos you must follows these steps:

step 1: figure out the which quadrant the angle is in. (if given a fraction with pi, use pi as 180 and find your angle)
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, plug it into the trig chart. If it is not on the trig chart then leave it as is or plug it into your calculator.

(*HINT: 0 degrees= 0; 30 degrees- pi/6; 45 degrees- pi/4; 60 degrees- pi/3; 90 degrees- pi/2*

Ex:Find the reference angle for sin 6pi/5
sin (6 x 180)/5 = 1080/5 = 216(treat pi as 180)-sin 216
this angle would be in the III quadrant because it is between 180 and 270
it would also be negative because y is negative in this quadrant.
216-180= 36(subtract from 180)

So, your final answer would be -sin36 degrees.