3. What is triangle?
A triangle is a polygon
with three edges and
three vertices. It is one of
the basic shapes in
geometry. A triangle with
vertices say A, B, and C is
denoted ΔABC.
4. Types of triangle
• Triangles are classified on the basis of:
– Sides
– Angles
5. Types of triangle on the basis of
sides
• Equilateral triangle
• Isosceles triangle
• Scalene triangle
6. Equilateral triangle
• It has 3 equal sides.
• It has 3 equal angles.
• Since the sum of the interior angles is 180
degrees, every angle of an equilateral
triangle is 60 degrees.
• It is a regular polygon with 3 sides.
• The altitude and median from a vertex is
the same single line.
• The ortho-centre and centroid of the
triangle is the same point.
7. Isosceles triangle
• It has two equal sides.
• It has two equal angles, that is, the base
angles.
• When the third angle is 90 degrees, it is
called a right isosceles triangle.
• The altitude from the apex to the base
bisects the angle at the apex.
8. Scalene triangle
• It has no equal sides, i.e. all the sides are
unequal.
• All the three angle are unequal, but the
sum of all the angle is 180 degree
9. Closure
So, studied today we studied about:
• Triangle
• Classification of triangle on basis of:
– Sides
– Angles
• Types of triangle on basis of sides:
• Equilateral triangle
• Isosceles triangle
• Scalene triangle
