3 ESERCIZI Parallelismo e perpendicolarità PRACTICE WITH CLIL Determining the locus A geometric locus (or, simply, locus) is a geometric shape in the Euclidean plane that is a subset of the points in the plane satisfying some property. Therefore: Each point that does not belong to the locus does not satisfy its specific property; Each point that does not satisfy its specific property does not belong to the locus. Problem Determine the locus of equidistant points from two given points. Theorem no.20, which we have studied in this unit, says that in every isosceles triangle, the altitude and median are the same line segment. Hence: if P is equidistant from two points A and B, the triangle PAB is isosceles and so, being M the median of AB, the line segment PM is perpendicular (as altitude) of the line AB, right in its median; If P belongs to said axis, then in the triangle APB altitude and median are the same hence the triangle is isosceles: AP is congruent to BP and therefore is equidistant from the two given points. P M A B 121