Chapter 11-Angles comprises the description of an angle and its various types. An angle is nothing but formed by two rays that have the same initial or starting point. The symbol "∠" denotes an angle. Degrees are used to measure the angles. Angles are seen everywhere in our environment. The vertex and the arm are considered as the two parts of an angle. The two rays which are joined to form an angle are known as arms, and the common starting or initial point is known as the vertex. The vertex of an angle always lies on it.
Each shape consists of many types of angles. For example, a triangle consists of three angles, and a square consists of four angles. The number of angles usually depends on the shape.
Chapter 11- Angles further describes that angles can be categorized into interior and exterior angles. Interior angles are formed within or inside the shapes, whereas angles formed outside the figure between any side of a shape and a side extending from the adjoining side are known as exterior angles.
This chapter further discusses the types of angles that exist. Angles are generally Classified into 6 types based on their measurements. They are acute angle, obtuse angle, right angle, reflex angle, straight angle, and complete angle. The application of angles can be seen significantly in the hands of the clock. Acute and obtuse angles are those which have the measurement between 0° to 90° and 90° and 180° respectively. Right angle and straight angle are identified by exact measurement of 90° and 180°, respectively, whereas complete angle is formed by only one ray which has a complete angle of 360°.