Gina wrote the following paragraph to prove that the segment joining the midpoints of two sides of a triangle is parallel to the third side. Given: ∆ABC Prove: The midsegment between sides and is parallel to side .
parallel to side ac
Draw ∆ABC on the coordinate plane with point A at the origin (0, 0). Let point B have the ordered pair (x1, y1) and locate point C on the x-axis at (x2, 0). Construct point D so it is the midpoint of . Point D has coordinates at by the Distance between Two Points Postulate. Construct point E so it is the midpoint of . The ordered pair of point E is by the Distance between Two Points Postulate. The slope of is found to be 0 through the application of the slope formula: When the slope formula is applied to , its slope is also 0. Since the slope of and are identical, and are parallel by the definition of parallel lines
what is the flaw in ginas proof The slope of segments DE and AC is not 0. Segments DE and AC are parallel by construction. The ordered pairs of D and E were found using the Midpoint Formula. Gina cannot construct the midpoint of a segment.
these are it i think there in order from the paragraph http://learn.flvs.net/webdav/assessment_images/educator_geometry_v14/1001/1001_G4_Q11b.gif
http://learn.flvs.net/webdav/assessment_images/educator_geometry_v14/1001/1001_G4_Q11d.gif
http://learn.flvs.net/webdav/assessment_images/educator_geometry_v14/1001/1001_G4_Q11f.gif
http://learn.flvs.net/webdav/assessment_images/educator_geometry_v14/1001/1001_G4_Q11h.gif
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