1. TRIANGLE A triangle is a simple closed curved made of three segments. A triangle has three sides and three angles , and all three sides and angles are called six elements of the triangle. A CB

2. TYPES OF TRIANGLES ON THE BASIS OF SIDES Scalene triangle-If all the sides of triangle are unequal they are called scalene triangle. Isosceles triangle-If any two sides of a triangle are Equal called isosceles triangle. Equilateral triangle-If all the sides of triangle are equal it is called equilateral triangle. 3. TYPES OF ANGLES ON THE BASIS OF ANGLES Acute angled triangle-If all the three angles of a triangle are acute it is called acute angled triangle. Right angled triangle-If one angle of a triangle is a right angle it is called right angled triangle. Obtuse angled triangle- if one angle of a triangle is obtuse it is called obtuse angled triangle. 4. MEDIANS OF A TRIANGLE The line segment joining a vertex of a triangle to the midpoint of the opposite side is called a median of a triangle. Altitudes of a triangle The Perpendicular line segment from a vertex of a triangle to the opposite side is called an altitude of the triangle. 5. PROPERTIES OF A TRIANGLE Exterior angles of a triangle An exterior angle + adjacent interior = 180 An exterior angle of a triangle is equal to sum of its two interior opposite angles. 6. ANGLE PROPERTY OF A SPECIAL TRIANGLE Isosceles triangle A triangle in which length of two sides are equal called isosceles triangle. In a triangle the angles opposite sides are equal. In a triangle the sides opposite equal angles are equal. 7. EQUILATERAL TRIANGLE A triangle in which all the three sides are of equal length is called an equilateral triangle. Sum of two sides of triangle The sum of the length of any two sides of the triangle 8. PYTHAGORAS PROPERTY In a right angled triangle the square of the hypotensure is equal to the sum of the squares of the other two sides. In this fig. ab + bc =ac 9. FINISHING OF PRESENTATION