Basic Concept Angle

In geometric studies, angles are defined as the result of rotation from the initial side to the terminal side. In addition, the direction of rotation has meaning in angles. An angle marked "positive" if the direction of rotation is opposite to the clockwise rotation direction and marked "negative" if the direction of rotation is clockwise. The direction of rotation to form an angle can also be observed at the end side position against the starting side. To make it easy, let's look at the following description:

In the field of Cartesian coordinates, if the initial side of a line coincides with the x-axis and the terminal side lies in one of the quadrants in the cartesian coordinate, it is called the standard angle. If the end side is on one axis of the coordinate, this angle is called quadrant limiting, ie 0°, 90°, 180°, 720°, and 360°.

Note that in order to express an angle, it is commonly used in Greek letters such as α (alpha), β (betha), γ (gamma), and θ (tetha), and capital letters such as A, B, C, and D.

Pay attention to the image below:
If the resulting angle is α (standard angle), then the angle β is called the coterminal angle, so that α + β - 360°, as illustrated as follows:

1. Standard angle and coterminal angle

2. The angle on each quadrant

Definition:
The coterminal angle is the standard two angles, having the coinciding ends.

Example:
Draw the standard corner angle from 60 ° and determine the position of each corner on the Cartesian coordinate!

Answer:

The starting side lies on the x-axis and the end side of OA is located in quadrant I.

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