The Pythagorean theorem is used to find the length of a line segment based on its coordinates:
d = √((x2-x1)² +(y2-y1)²)
AB = √((-1-4)² +(4-(-1))²) = √50 ≈ 7.1
BC = √((0-(-1))² +(-3-4)²) = √50 ≈ 7.1
CA = √((4-0)² +(-1-(-3))²) = √20 ≈ 4.5
Adding these numbers for the side lengths, we get
P = 7.1 + 7.1 + 4.5 = 18.7
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Saving rounding until the end, as we should, the result would be 18.6. The instructions specifically tell us not to do that.
