This is the write-up of Assignment #9 |
Brian R. Lawler
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EMAT 6680 |
01/02/01
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See the Definition and Construction of a Pedal Triangle | |
II.
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Exploring conditions of the Pedal Triangle |
Considering various loci and traces |
(Click on image to explore in Geometer's Sketchpad.)
2. | What if pedal point P is the centroid of triangle ABC? | |
When the pedal point is located at the centroid of triangle ABC, it appears that the pedal triangle will always exist inside the original triangle. | ||
3. | What if . . . P is the incenter . . . ? | |
When the pedal point is located at the incenter of triangle ABC, points R, S, and T lie at the points of tangency of triangle ABC's incircle. Thus, this incircle is also the circumcircle of triangle RST. | ||
4. | What if . . . P is the Orthocenter . . . ? Even if outside ABC? | |
When the pedal point is located at the orthocenter of triangle ABC, the points R, S, T occur at the intersection of triangle ABC's sides and altitudes. | ||
5. | What if . . . P is the Circumcenter . . . ? Even if outside ABC? | |
When the pedal point is located at the circumcenter of triangle ABC, the points R, S, T occur at the midpoints of triangle ABC's sides. | ||
6. | What if . . . P is the Center of the nine point circle for triangle ABC? | |
Recall triangle ABC must be acute for the nine point center to exist. When the pedal point is located at this center, the points R, S, and T all lie on the sides of triangle ABC. | ||
7. | What if P is on a side of the triangle? | Click here to investigate the GSP file. |
Again, R, S, and T will always remain on triangle ABC. | ||
8. | What if P is one of the vertices of triangle ABC? | |
9. | Find all conditions in which the three vertices of the Pedal triangle are colinear (that is, it is a degenerate triangle). This line segment is called the Simson Line. | |
The pedal triangle degenerates as P becomes one of the points A, B, or C. |
Comments? Questions? e-mail me at blawler@coe.uga.edu |
Last revised: January 2, 2001 |