Initial side

Definition

The initial side of an angle is the fixed ray where the measurement of the angle begins. It is often positioned along the positive x-axis in standard position.

5 Must Know Facts For Your Next Test

1. The initial side remains stationary while the terminal side rotates to form an angle.
2. In standard position, the initial side lies on the positive x-axis.
3. The measurement of angles starts from the initial side and moves counterclockwise for positive angles and clockwise for negative angles.
4. The location of the initial side helps in determining reference angles on the unit circle.
5. The concept of initial and terminal sides is crucial for understanding trigonometric functions.

Review Questions

• What is the position of the initial side when an angle is in standard position?
• How does one determine whether an angle is positive or negative with respect to its initial side?
• Why is knowing the location of the initial side important in trigonometry?

Related terms

Terminal Side: The ray that rotates from the initial side to form an angle, completing its measure.

Standard Position: An angle positioned such that its vertex is at the origin and its initial side lies along the positive x-axis.

Reference Angle: \( A smaller angle formed by a terminal side and the x-axis, used to simplify calculations in trigonometry. \)