The following is an incorrect flowchart proving that point L, lying on line LM which is a perpendicular bisector of segment JK, is equidistant from points J and K:

Segment JK intersects line LM at point N.

Line LM is a perpendicular bisector of segment JK; Given. Two arrows are drawn from this statement to the following two statements. Segment JN is congruent to segment NK; Definition of a Perpendicular Bisector. Angle LNK equals 90 degrees, and angle LNJ equals 90 degrees; Definition of a Perpendicular Bisector. An arrow is drawn from this last statement to angle LNK is congruent to angle LNJ; Definition of Congruence. Segment LN is congruent to segment LN; Reflexive Property of Equality. Draw segment JL and segment KL; by Construction. Four arrows from the previous four statements are drawn to the statement triangle JNL is congruent to triangle KNL; Side Angle Side, SAS, Postulate. An arrow from this statement is drawn to the statement segment JL is congruent to segment KL; Corresponding Parts of Congruent Triangles are Congruent CPCTC. An arrow from this statement is drawn to JL equals KL; Definition of Congruence. An arrow from this statement is drawn to Point L is equidistant from points J and N; Definition of Equidistant.

What is the error in this flowchart?

JL and KL are equal in length, according to the definition of a midpoint.
Point L is equidistant from endpoints J and K, not J and N.
The arrow between ΔJNL ≅ ΔKNL and segment J L is congruent to segment K L points in the wrong direction.
An arrow is missing between the given statement and ∠LNK ≅ ∠LNJ.

1 answer

The error in this flowchart is that JL and KL are equal in length, not LN. The correct statement should be that segment LN is congruent to segment LN, not segment JL is congruent to segment KL.