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Cevians AD and BE meet at point X inside triangle ABC. CX extended meets AB at F. If [AEX] = [CEX] = [CDX] = [BDX] = [BXF] = [AXF],  (<--- areas)

must X be the centroid of triangle ABC?

 May 21, 2021

Best Answer 

 #1
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The answer is yes; line segments AD, BE, and CF would have to be medians, which would by definition make X the centeroid, if the following pairs of triangles have the same area

:\(\Delta AXF\ and\ \Delta FXB\)

\(\Delta AXE\ and\ \Delta EXC\)

\(\Delta BXD\ and\ \Delta DXC\)

Let's look at the reasoning for the last pair; the other two would be similar.

The line segment \(X{H}_{3}\)is perpendicular to BC, so it must be perpendicular to BD and DC both; So it would serve as a heigt for triangles BXD and DXC. If the two triangles have the same height and the same area, it follows that they have the same base; that is, the line segments BD and DC must have the same length. In other words AD is a median.

 May 21, 2021
 #1
avatar
0
Best Answer

 

The answer is yes; line segments AD, BE, and CF would have to be medians, which would by definition make X the centeroid, if the following pairs of triangles have the same area

:\(\Delta AXF\ and\ \Delta FXB\)

\(\Delta AXE\ and\ \Delta EXC\)

\(\Delta BXD\ and\ \Delta DXC\)

Let's look at the reasoning for the last pair; the other two would be similar.

The line segment \(X{H}_{3}\)is perpendicular to BC, so it must be perpendicular to BD and DC both; So it would serve as a heigt for triangles BXD and DXC. If the two triangles have the same height and the same area, it follows that they have the same base; that is, the line segments BD and DC must have the same length. In other words AD is a median.

Guest May 21, 2021

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