# NCERT Solutions Class 7 Maths Triangle and its properties

## NCERT Solutions Class 7 Maths Triangle and its properties

In the previous article for Class 7 Maths, we have discussed the Chapter 6 – Triangle and its properties. The topics covered were an introduction to the triangle, types of triangle, exterior angle of a triangle and its properties.

In this article, we will discuss the angle sum property from Class 7th Maths.

We already know that a plane figure surrounded by three line segments is called a triangle. It is donated by the symbol ∆.

Angle Sum Property

The total measure of the three angles of a triangle is 180°.

Given: -∠1,∠2,∠3 are angles of  ∆ABC

∠4 is the exterior angle when BC is extended to D

Justification ∠1+∠2=∠4(by exterior angle property)

∠1+∠2+∠3=∠4+∠3 (adding ∠3 on both sides)

∠4 and ∠3 form a linear pair so it is 180°

Hence ∠1+∠2+∠3=180°

Two Special Triangles: Equilateral and Isosceles

Equilateral Triangle: – Triangles in which all the three sides are equal are called an equilateral triangle.

Two Important points:-

• all sides have the same length
• each angle has measure 60°

Isosceles triangle: – Triangles in which two sides are of equal lengths is called an isosceles triangle.

Two Important points:-

• two sides have the same length
• base angles opposite to the equal sides are equal

For examples and practice questions click on Math Class 7.

Sum of the lengths of two sides of a triangle:-

• Sum of lengths of any two sides of a triangle is greater than the third side

Right-angled triangle and Pythagoras property

Pythagoras property is found by a Greek philosopher Pythagoras.

In a right-angled triangle, the sides have different names

The side opposite to the right angle is called hypotenuse, the other two sides are called legs of the right-angled triangle

It states that for any right-angled triangle, the area of the square on the hypotenuse equal to the sum of the areas of the square on the legs.

The square on the hypotenuse = sum of the squares on the legs

a²=b²+c²

Maths NCERT solutions of Class 7 are available at Class 7 Maths.

## You can read more topics of Maths NCERT Solutions Class 7

Lines and Angles

Triangle and its properties

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August 29, 2019