A median connects the vertex of a triangle to the mid-point of the opposite side.
An altitude is a perpendicular line segment from one vertex to the opposite side of the triangle.
An exterior angle of a triangle is equal to the sum of its interior opposite angles.
A triangle having all three sides equal is called an equilateral triangle.
All three angles of an equilateral triangle are equal to 60o.
A triangle having two equal sides is called an isosceles triangle.
In an isosceles triangle, base angles opposite to the equal sides are equal.
SUM OF TWO SIDES
The sum of the length of any two sides is greater the length of the third side.
The difference between the lengths of any two sides is smaller than the length of the third side.
RIGHT ANGLED TRIANGLE
In a right angled triangle, the side opposite to the right angle is called the hypotenuse and the other two sides are called legs.
According to Pythagoras theorem, the square of the hypotenuse is equal the sum of the squares of the other two sides.