Question 1173060
the reference angle is the equivalent angle in the first quadrant.


2pi/3 is in the second quadrant.


the equivalent angle in the first quadrant is pi - 2pi/3 = 3pi/3 - 2pi/3 = pi/3.


the reference number is t = pi/3.


this may be easier to understand in degrees.


radians * 180 / pi = degrees.


2pi/3 * 180 / pi = 2/3 * 180 = 120 degrees.


that's in the second quadrant.


the reference angle is the equivalent angle in the first quadrant.


the equivalent angle in the first quadrant is equal to 180 minus 120 = 60 degrees.


the equivalent angle in radians is 60 * pi / 180 = 1/3 * pi = pi/3.


your reference angle is pi/3 = t


t is the lower case of T.