This document defines and describes the six main types of triangles: equilateral, isosceles, scalene, right, obtuse, and acute. An equilateral triangle has all three sides the same length and all three interior angles measuring 60 degrees. An isosceles triangle has two sides of equal length and two equal angles. A scalene triangle has all three sides and angles of different measures. A right triangle contains one 90 degree angle. An obtuse triangle has one interior angle greater than 90 degrees, and an acute triangle has all interior angles less than 90 degrees.

1. A triangle is a polygon with three edges and
three vertices. It is one of the
basic shapes in geometry.

3.  Equilateral Triangle
 Isosceles Triangles
 Scalene Triangles
 Right Angle Triangles
 Obtuse Triangles
 Acute Triangles

4. An equilateral triangle has all sides the
same length. An equilateral triangle is
also a regular polygon with all angles
measuring 60°.

5. Equilateral Triangles

6. An isosceles triangle has two sides of
equal length. An isosceles triangle also
has two angles of the same measure,
namely the angles opposite to the two
sides of the same length

7. Isosceles Triangle

8. A scalene triangle has all its sides of
different lengths. Equivalently, it has all
angles of different measure.

9. Scalene Triangle

10. A right triangle (or right-angled triangle,
formerly called a rectangled triangle) has
one of its interior angles measuring 90°
(a right angle). The side opposite to the
right angle is the hypotenuse, the longest
side of the triangle.

11. Right Angle Triangle

12. A triangle with one interior angle
measuring more than 90° is an obtuse
triangle or obtuse-angled triangle.

13. Obtuse Triangle

14. A triangle with all interior angles
measuring less than 90° is an acute
triangle or acute-angled triangle.

15. Acute Triangle