d ( AC ) = 6 ( because A and C have the same y-coordinate )
d ( AB ) = √[(x2 - x1)² + (y2 - y1)²],
where A ( x1, y1 ) = ( -3, 1 ) and B ( x2, y2 ) = ( -1, 3 )
d ( AB ) = √[(-1 -(-3))² + (3 - 1 )²] = √[(-2)² + 2²] = √8 = 2√2
d ( BC ) = √[(3-(-1))² + (1-3)² =√[4² + (-2)²]= √20 = 2√5
The perimeter of ΔABC:
6 + 2√2 + 2√5 = 6 + 2 · 1.41 + 2 · 2.24 =
= 6 + 2.82 + 4.48 = 13.30
