Question:
What is the area of the triangle formed by the points O (0, 0), A (6, 0) and B (0, 4)?
Solution:
The given triangle $\Delta \mathrm{OAB}$ is a right angled triangle, right angled at $O$. the co-ordinates of the vertices are $O(0,0) A(6,0)$ and $B(0,4)$.
So,
Altitude is 6 units and base is 4 units.
Therefore,
$\operatorname{ar}(\Delta \mathrm{OAB})=\frac{1}{2}($ Base $)($ Altitude $)$
$=\frac{1}{2}(4)(6)$ sq. units
$=12$ sq. units