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MATHEMATICS Chapter 5: Understanding Elementary Shapes
(1) UNDERSTANDING ELEMENTARY SHAPES 05 UNDERSTANDING ELEMENTARY SHAPES Measuring Line Segments A ruler or a divider is generally used to find the lengths of line segments. The length of a line segment can be defined as the distance between its endpoints. Angles and its Types An angle is made up of any two rays which have the same endpoint or starting point. It can be better understood by the movement of clock-hands. When a clock hand moves, it forms an angle. To measure the angle, a protractor is used. It should be noted that a straight angle is 180 degrees while a right angle is 90 degrees. Based on the degree, an angle can be classified into 3 main types: • Acute angle: When an angle measure is less than a right angle, it is called an acute angle. • Obtuse angle: When an angle measure more than a right angle but less than a straight angle, it is called an obtuse angle. • Reflex angle: When an angle measure more than a straight angle, it is called a reflex angle. It should be noted that two intersecting lines are perpendicular if the angle formed
(2) UNDERSTANDING ELEMENTARY SHAPES 05 between them is 90 degrees. Triangles and its Types A triangle is a closed figure having three sides and three interior angles. A triangle can be classified based on its length of sides and by its angles. The detailed classification of triangles is given below. Based on Triangle Name Description Based on its sides Scalene triangle All three sides are unequal. Isosceles triangle Any two sides are equal. Equilateral triangle All three sides are equal. Based on its angles Acute angled triangle All the angles are acute. Right-angled triangle Anyone angle is the right angle. Obtuse angled triangle Anyone angle is obtuse. Polygons
(3) UNDERSTANDING ELEMENTARY SHAPES 05 Polygons are closed geometric shapes having at least 3 sides and 3 angles. Based on the number of sides, a polygon can be categorized into multiple types. Some of the most common polygons are: Polygon Name No. of Sides Triangle 3 Quadrilateral 4 Pentagon 5 Hexagon 6 Heptagon 7 Octagon 8 Nonagon 9 Decagon 10 Quadrilaterals