Question

lab activity on angle sum property maths class 9​

Answer 1

Answer:

For straight line angle refer to Activity 11. Triangle A plane figure closed by three intersecting lines is called a triangle, here Tri' means 'three'. A ...

Answer 2

$\huge⚘ \bf \ \red{Answer}$

$\bf \underline\blue{objective}$

To verify that the sum of the angles of a triangle is 180°.

$\bf \underline\blue{materials \: required}$

• Cardboard sheet

• White chart paper

• Geometry box

• Scissors

• Adhesive

• Drawing sheet

• Tracing paper

$\bf \underline\blue{Prerequisite \: Knowledge}$

• Knowledge of straight angle

• Concept of triangle and its properties

$\bf \underline\blue{theory}$

• For straight line angle refer to Activity 11.

$\bf \underline\blue{triangle}$

A plane figure closed by three intersecting lines is called a triangle, here Tri’ means ‘three’. A triangle has three sides, three angles and three vertices and it is denoted by the symbol ‘Δ’. A ΔABC is shown in Fig. 12.1.

Some basic properties of triangles

are given below :

• The sum of all the angles of a triangle is always 180°.

• Angles opposite to equal sides of a triangle are equal.

• The sides opposite to equal angles in a triangle are equal.

• In a triangle, the angle opposite to longer side is larger and vice-versa.

• The sum of two sides of a triangle is greater than the third side.

• The exterior opposite angle in a triangle is equal to sum of opposite interior angles.

Note: The property (1) is called Angle Sum Property of triangle.