**Note :**

a) if an area of a triangle is given then use ± sign.

b) if points P, Q & R are collinear , then area of triangle is zero.

Condition for three points to be collinear :

If the area of triangle is zero then all points must be collinear .

Types of Triangle :

1.Equilateral Triangle : all sides are equal

2.Isosceles Triangle : two sides are equal

3.Right-angled Triangle : two sides are perpendicular i.e one of them angle is 90°.