For ΔABC,
AC2 = AB2 + BC2
(5)2 = (3)2 + (4)2
Therefore, ΔABC is a right-angled triangle, right-angled at point B.
Area of ΔABC = 1/2 x AB x BC = 1/2 X 3 X 4 = 6CM2
For ΔADC,
Perimeter = 2s = AC + CD + DA = (5 + 4 + 5) cm = 14 cm
s = 7 cm
By Heron’s formula,
Area of ABCD = Area of ΔABC + Area of ΔACD
= (6 + 9.166) cm2 = 15.166 cm2 = 15.2 cm2 (approximately)