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GeoGebraGeoGebra Lesson

Loci

PART ONE

Describe the perpendicular bisector as a locus of points:

Describe the angle bisector as a locus of points:

Constructions

Let r, s be two lines and let A, B be two points. Find the locus of the points equidistant from both r and s, and both A and B.

a)

About construction a) :

Describe the locus:

b.

About construction b) :

Describe the locus:

PART TWO

Describe the circumference as a locus of points:

How many circumferences pass through the three points?

Select all that apply
  • A
  • B
  • C
  • D
  • E
Check my answer (3)

Let's check your answer in the case below:

  1. Find the locus of points equidistant from both A and B;
  2. Find the locus of points equidistant from both B and C;
  3. Find the intersection between the loci.

Are A, B and C equidistant from this intersection? Why?

So, can you say how many circumferences pass through A, B and C at the same time? Use the definition of circumference as locus of points to explain.

how many circumferences pass through three collinear points?

Select all that apply
  • A
  • B
  • C
  • D
  • E
Check my answer (3)

How many circumferences pass through two points?

why?