- The Sum of all angles in a triangle is 180 degrees.
- An angle less than 90 degrees is called an Acute angle.
- An angle greater than 90 degrees is called an Obtuse angle.
- The Sum of any two sides of a triangle is always greater than the third side.
- A triangle with two sides equal is called an Isosceles triangle. The two angles of an isosceles triangle that are not contained between the equal sides are equal.
- A triangle with all sides equal is called an Equilateral triangle. All angles of an equilateral triangle equal 60 degrees.
- A triangle with all sides unequal is called a Scalene triangle.
- If in a triangle all of its angles are less than 90 degrees then that triangle is called an Acute-angled triangle.
- A triangle with one of its angles equal to 90 degrees then that triangle is called a Right-angled triangle.
- A triangle with one of its angles greater than 90 degrees then that triangle is called an Obtuse-angled triangle.
- If one side of a triangle is produced, then that exterior angle formed is equal to the sum of the opposite remote interior angles.
- The Sum of any two sides of a triangle is always greater than the third side.
-The difference between any two sides of a triangle is always less than its third side.
-If a, b, and c are the sides of a triangle and c is the largest side, then:
1. Acute Angled Triangle: c$$^2$$ < a$$^2$$ + b$$^2$$
2. Right Angled Triangle: c$$^2$$= a$$^2$$ + b$$^2$$
3. Obtuse Angled Triangle: c$$^2$$ > a$$^2$$ + b$$^2$$
