The sides of a right triangle are 5cm, 12 cm and 13 cm. Then its area is

$\therefore a^2+b^2=5^2+{12}^2=25+144=169$

$c^2={13}^2=169$

$\therefore c^2=a^2+b^2$

$\therefore \Delta ABC$  is a right angled triangle

Area $=\frac{1}{2}ab=\frac{1}{2}\times 5\times 12=30c{m}^2$

$=0.003m^2$