What is Angles ? question and answer !

Angles

An angle is the union of two non-collinear rays with a common initial point.

the two rays forming an angle are called the "arms" of the angle and the common initial point is called the "vertex" of the angle.

The angle formed by the rays AB and AC as shown in images and denoted by the angle BAC or angle CAB.

What is Angles ? question and answer !

For the sake of convenience the angle, angle BAC or angle CAB can also be referred simply as angle A however, this cannot be done if there are more than one angle with the same vertex A. In such cases we can denote the angles by the symbols such as angle 1, angle 2, angle 3, etc like as shown in images in downword.

What is Angles ? question and answer !

Divides the plane containing it into two parts (1) the part of the plane which lies between the rays AB and AC and (11) the part of the plane which does not lie between the rays AB and AC. The first part is known as the interior of angle BAC and the second part is the exterior of angle BAC as defined in image.

Interior of an angle

The interior of an angle BAC is the set of all points in its plane, which lie on the same side of AB as C and also on the same side of AC as B.

What is Angles ? question and answer !

Exterior of an angle

The exterior of an angle BAC is the set of al points in its plane, which do not lie on the angle or in its interior.

NOTE : - It should be noted that angle BAC, interior of angle BAC and exterior of  angle BAC are disjoint sets, for example the intersection of any two of these three is the empty set, The unior of these three  is the whole plane containing angle BAC.

Congruent angles

The angles are said to be congruent if a trace copy of one can be superposed on the other to cover it, completely an exactly.

If angle BAC is congruent of angle FEG, then we write angle BAC = angle FEG. congruent angles will be called equal angles and we shall write angle BAC = angle FEG instead of writing angle BAC = angle FEG.