This week in Precalculus 11, we reviewed and learned about trigonometry. We learned about quadrants, the initial arm, the terminal arm, the rotation angle, reference angle, and the coterminal angle. The rotation angle is formed between the initial arm (x-axis on the positive side) and the terminal arm. The reference angle is the angle touching the x-axis and the terminal arm.

*Reference angle can never be over 90°.

Ex.

To find the reference angle, subtract the bigger number with the x-axis number. In this case, you have to subtract 180° from 200° but hypothetically, if the rotation angle was 320°, you would have to subtract 320° from 360°.

To find the coterminal angle, you have to subtract the rotation angle from 360°. In this example, we subtract 200° from 360°. The coterminal angle is negative because it is going the opposite way (clockwise).