Fie D(3;3)
In tr. BDC, unghiul BDC=90°
A=BD×DC/2
A=6×3/2
A=18/2=9
In tr. ADC, unghiul ADC=90°
A=AD×DC/2
A=2×3/2
A=6/2=3
Aria BAC= Aria BDC - Aria ADC = 9-3=6
