The acute angle between the terminal side of and the x-axis is called the reference angle for .

For example:

1st Quadrant	2nd Quadrant
3rd Quadrant	4th Quadrant

Remember from Technical Mathematics 1 that the signs of the trigonometric functions depend on the quadrant.

Sin and Csc are positive.	All are positive.
Tan and Cot are positive.	Cos and Sec are positive.

Use this as a memory aid: All Students Take Calculus.

tan 300°

	300° is in the 4th quadrant, so the answer will be negative.

(It should be 300° not 310°)

sec 225°

	225° is in the 3rd quadrant, so the answer will be negative.

sin 163°

	163° is in the 2nd quadrant, so the answer will be positive.
Ref = 180° - 163° = 17° You can use a calculator to find the answer which is 0.292.