User:RALmath/sandbox

Article Evaluation

Article: Parallel Postulate

Questions for evaluation:

• Is everything in the article relevant to the article topic? Is there anything that distracted you?
• The content all seems relevant to the topic of Euclid's 5th axiom, giving a thorough explanation of the history of those who have tried to prove or disprove it and the results that arose from these attempts. I thought the included images helped to illustrate the ideas and were effective for the article. I did become distracted by the citation jumble in the introduction section. There was also information about the postulate not relating to parallel lines, bu rather parallelism which I think should be explained in more depth.
• Is any information out of date? Is anything missing that could be added?
• As far as mathematical content goes, I think the information is still relevant even if it is from Euclid's original writing. The content is up-to-date and covers the history adequately.
• What else could be improved?
• I think the addition of a section illustrating the three cases for the parallel postulate, the acute, obtuse, and equal cases, would help the reader make that distinction rather than only the sentence at the end of the history section. A more thorough explanation of the critique stated to help the reader understand the situation would be useful as well.
• Is the article neutral? Are there any claims that appear heavily biased toward a particular position?
• The article appears neutral, not biased toward a particular side and sharing multiple aspects of the work occurring around the postulate.
• Are there viewpoints that are overrepresented, or underrepresented?
• The viewpoints are equally represented in a neutral tone.
• Do the links work? Does the source support the claims in the article?
• Yes, all the links which I tried worked, attached to the appropriate article, and supported the claims made by the linking article.
• Is each fact referenced with an appropriate, reliable reference? Where does the information come from? Are these neutral sources? If biased, is that bias noted?
• The definition in the lead section needs looked at for another citation. Some of the information is from Euclid's writing, The Elements, and from various other academic journals and books, These sources are neutral and unbiased in tone, giving even, accurate information which was included in the article. Any biased or questionable sources have been removed, from the descriptions given in the talk page.
• What kinds of conversations, if any, are going on behind the scenes about how to represent this topic?
• There are many talks for this page. Many have to do with changes made, citations which were not reliable, sections which readers found to be unnecessary, and areas where expansions should be considered. The conversations seemed to have sparked some much needed edits to the article and citations because I did not observe many of the talk topics calling for change within the article.
• How is the article rated? Is it a part of any WikiProjects?
• The article has a c class rating, is high priority, and is in the field of geometry. It is a part of a WikiProject.
• How does the way Wikipedia discusses this topic differ from the way we've talked about it in class?
• It goes into more depth, but I do remember the historical implication and arguments surrounding the postulate form the History of Mathematics course. The 3 versions of the postulate are accurate in comparison to what we learned in class however and give explanations of the differences.

Article Selection

Possible Topics: Spieker circles or Epispirals

I will be working from the stub articles already on Wikipedia to extend the scope of one of these articles.

The topic I have chosen to expand upon is Spieker circles due to the accessibility of resources for this related information as opposed to epispiral information.

References:

The Eperson-Spieker Circle- Bellew https://www.jstor.org/stable/3619628?read-now=1&loggedin=true&seq=1#page_scan_tab_contents

A generalisation of the Spieker circle and Nagel line- De Villiers

A treatise on the circle and the sphere- Coolidge

Episodes in Nineteenth and Twentieth Century Euclidean Geometry, Volume 37- Honsberger

Addition to the Spieker circle article

I will add the following content and citation to the Spieker circle stub article:

Spieker circles also have relations to Nagel points. The incenter of the Speiker circle and the Nagel point form a line within the Spieker circle. The middle of this line is the exact center of the Spieker circle.

Spieker Circles

Maintain the current lead section from the stub article and the accompanying image

History

The Spieker circle and Spieker center are named after Theodor Spieker, a mathematician and professor from Potsdam, Germany. In 1862, he published Lehrbuch der ebenen geometrie mit übungsaufgaben für höhere lehranstalten, dealing with planar geometry. Due to this publication, influential in the lives of many famous scientists and mathematicians including Albert Einstein, Spieker became the mathematician for whom the Spieker circle and center were named.

Construction

To find the Spieker circle of a triangle, the medial triangle must first be constructed from the midpoints of each side of the original triangle. The circle is then constructed in such a way that each side of the medial triangle is tangent to the circle within the medial triangle, creating the incircle. This circle center is named the Spieker center.

The Nagel point N of a triangle

Nagel points and lines

Spieker circles also have relations to Nagel points. The incenter of the triangle and the Nagel point form a line within the Spieker circle. The middle of this line segment is the Spieker center. The Nagel line is formed by the incenter of the triangle, the Nagel point, and the centroid of the triangle. The Spieker center will always lie on this line.

Nine-point circle and Euler line

The incircle and circumcircle of a triangle

Spieker circles were first found to by very similar to nine-point circles by Julian Coolidge. At this time, it was not yet identified as the Spieker circle, but is referred to as the "P circle" throughout the book. The nine-point circle with the Euler line and the Spieker circle with the Nagel line are analogous to each other, but are not duals, only having dual-like similarities. One similarity between the nine-point circle and the Spieker circle deals with their construction. The nine-point circle is the circumscribed circle of the medial triangle, while the Spieker circle is the inscribed circle of the medial triangle. With relation to their associated lines, the incenter for the Nagel line relates to the circumcenter for the Euler line. Another analogous point is the Nagel point and the othocenter, with the Nagel point associated with the Spieker circle and the orthocenter associated with the nine-point circle. Each circle meets the sides of the medial triangle where the lines from the orthocenter, or the Nagel point, to the vertices of the original triangle meet the sides of the medial triangle.

Example of a nine point conic, analogous to a Spieker conic

Spieker Conic

The nine-point circle with the Euler line was generalized into the nine-point conic. Through a similar process, due to the analogous properties of the two circles, the Spieker circle was also able to be generalized into the Spieker conic. The Spieker conic is still found within the medial triangle and touches each side of the medial triangle, however it does not meet those sides of the triangle at the same points. If lines are constructed from each vertex of the medial triangle to the Nagel point, then the midpoint of each of those lines can be found. Also, the midpoints of each side of the medial triangle are found and connected to the midpoint of the opposite line through the Nagel point. Each of these lines share a common midpoint, S. With each of these lines reflected through S, the result is 6 points within the medial triangle. Draw a conic through any 5 of these reflected points and the conic will touch the final point. This was proven by de Villiers in 2006.

The incircle (purple) and excircles (blue) to a triangle.

Spieker radical circle

The Spieker radical circle is the circle, centered at the Spieker center, which is orthogonal to the three excircles of the medial triangle.