The area A of the triangle two of whose vertices lie on the axes, with coordinates (a, 0) , (0, b), and a third vertex (c, d) is obtained from previous formula by a mere horizontal axis shift of -a units as A = |-ad + b(a - c)|/2

The area $A$ of the triangle two of whose vertices lie on the axes, with coordinates $(a, 0)$, $(0, b)$, and a third vertex $(c, d)$ is obtained from previous formula by a mere horizontal axis shift of -a units as $$A = \frac{|-ad + b(a - c)|}{2}$$