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°.