 # Triangles and Its Properties Class 7 Notes: Chapter 6

In chapter 6 of class 7 maths, various characteristics and properties of triangles are discussed. Let us look at a few important points about the triangle.

• A triangle is a closed curve made of three line segments.
• It has three sides, three vertices and three angles.
• In a triangle, the line segment joining a vertex to its opposite sides is known as a median. A triangle has 3 medians.
• The perpendicular line segment joining a vertex of a triangle to its opposite side is
called an altitude of the triangle. A triangle has 3 altitudes.
• The total measure of the three angles at the vertex is 180°. This is known as the angle sum property of the triangle.
• When all the sides of the triangle have the same length, then the triangle is said to be an equilateral triangle.
• When only two sides of the triangle have the same length, then the triangle is said to be an isosceles triangle. The unequal side of an isosceles triangle is known as the base.
• The side opposite to the right angle of a right-angled triangle is called the hypotenuse
and the other two sides are known as its legs.

## Properties of a Triangle

### Property of the lengths of sides of a triangle

• The sum of the lengths of any two sides of a triangle is greater than the length of the third side.
• The difference between the lengths of any two sides of a triangle is lesser than the third side. This property is useful in knowing if it is possible to draw a triangle when the lengths of the three sides are known.

### Pythagoras property

• In a right-angled triangle, the square of the hypotenuse is equal to the sum of the square on its legs.

Square of the hypotenuse = Sum of the square on its legs

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