Angle is discussed here in details. In our daily life we come across different objects having two arms hinged at a point. For example, hands of a clock, two arms of a divider, and two sharp edges of a scissors are all hinged at a point and thus are inclined to each other. This inclination between two arms is known as angle.
When two rays have a common end point they from an angle. In this figure two rays OA and OB have a common end point O. So they form an angle AOB. The common end point is called the Vertex and rays OA and OB are the arms of the angle.
In the above figure, AOB is angle whose two arms are the rays OB and OA. The symbol for an angle is < and angle AOB can be written as <AOB. Every angle has a measure. The unit of measurement of an angle is degree (°). In a figure the measure of an angle is generally written between the arms of the angle, close to the vertex.
Let us take two strips of a thick cardboard and place them one top of the other as shown in the figure. If we hold the two strips at one end and rotate one of the strip, we can form different angles.
We assume the strips as two rays meeting at a point. The point where the rays meet is called the vertex. Two rays are called the sides or arms of the angle. In the given figure XY and YZ are two rays meeting at a common end point Y. The point Y where the angle is formed, is the vertex of the angle.
The angle is represented by the symbol ∠. The angle is read as ∠XYZ. We measure an angle in degrees.
Always remember, while naming the angle, the vertex is always in the centre.
The figure formed by two rays with the same initial point is called an angle.