Access Point #: MAFS.912.G-CO.4.AP.12e Archived Access Point

Construct perpendicular lines, including the perpendicular bisector of a line segment.

Clarifications:

Essential Understandings

Concrete:

  • When given a line segment, use manipulatives (e.g., ruler, compass, string, reflective devices, paper folding, dynamic geometric software, etc.) to bisect the given segment forming perpendicular lines.

    Image of a bisected angle.
  • Place compass point on A and stretch the compass MORE THAN half way to point B, but not beyond B.

  • With this length, swing a large arc that will go BOTH above and below begin mathsize 12px style stack A B with bar on top end style.
  • Without changing the span on the compass, place the compass point on B and swing the arc again. The two arcs that have been created should intersect.

  • With a straightedge, connect the two points of intersection.

  • This new straight line bisects begin mathsize 12px style stack A B with bar on top end style.
  • Label the point where the new line and begin mathsize 12px style stack A B with bar on top end style cross as C.
  • begin mathsize 12px style stack A B with bar on top end style has now been bisected and AC = CB. (It could also be said that the segments are congruent, begin mathsize 12px style stack A C with bar on top space approximately equal to space stack C B with bar on top end style)
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Representation:
  • Understand the following concepts and vocabulary: perpendicular, bisector, line segment and midpoint.
  • Perpendicular lines are two lines that cross forming 90° angles.
  • A perpendicular bisector is a perpendicular line or a segment that passes
General Information

Number: MAFS.912.G-CO.4.AP.12e

Category: Access Points

Date Adopted or Revised: 07/14

Cluster: Make geometric constructions. (Geometry - Supporting Cluster) :  Clusters should not be sorted from Major to Supporting and then taught in that order. To do so would strip the coherence of the mathematical ideas and miss the opportunity to enhance the major work of the grade with the supporting clusters.

This access point is part of these courses.