A ( -1 , 3)
B ( 2 , -1)
C ( 3 , 6)
AB= √ [ ( 2+1)² + ( -1-3)²]
AB= √(9+16)
AB= √ 25
AB= 5
BC= √ [ ( 3-2)²+ ( 6+1)²]
BC= √ ( 1+ 49)
BC= √50
BC= 5√ 2
AC= √ [ (3+1)²+ ( 6-3)²]
AC= √ (16+9)
AC= √25
AC = 5
(5√2)²=5²+5²
25•2=25+25
50=50=> ∆ ABC= dreptunghic isoscel
Aria = AB• AC/2
Aria= 5•5/2
Aria=25/2
Aria=12,5 um²