RBSE Class 7 Maths Notes Chapter 6 The Triangles and Its Properties

These comprehensive RBSE Class 7 Maths Notes Chapter 6 The Triangles and Its Properties will give a brief overview of all the concepts.

RBSE Class 7 Maths Chapter 6 Notes The Triangles and Its Properties

→ A triangle is a simple closed curve made of three line-segments.

→ It has three vertices, three sides and three angles. The six elements of a triangle are its three angles and the three sides.

→ The line segment joining a vertex of a triangle to the mid-point of its opposite side is called a median of the triangle. A triangle has 3 medians. The point of concurrence of three medians is called centroid.

→ The perpendicular line segment from a vertex of a triangle to its opposite side is called an altitude of the triangle. A triangle has 3 altitudes. The point of concurrence of three altitudes is called ortho centre.

→ An exterior angle of a triangle is formed, when a side of a triangle is produced.

→ The measure of any exterior angle of a triangle is equal to the sum of the measures of its interior opposite angles.

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

→ A triangle is said to be equilateral, if each one of its sides has the same length. In an equilateral triangle, each angle has measure 60°.

→ A triangle is said to be isosceles, if at least any two of its sides are of same length. The non-equal side of an isosceles triangle is called its base. The base angles of an isosceles triangle have equal measure.

→ 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 is smaller than the length of the third side.

→ In a right-angled triangle, the opposite side of the right angle is called the hypotenuse and the other two sides are called its legs.

→ Pythagoras property: In a right-angled triangle the square on the hypotenuse = the gum of squares on its legs (a² = b² + c²).

→ If a triangle is not right-angled, this property does not hold good.

• If all the three angles of a triangle are acute, then (it is called acute-angled triangle.
• If one angle of a triangle is 90°, then it is called right-angled triangle.
• If one angle of a triangle is obtuse, then it is called obtuse-angled triangle.