Powers Great and Small

I enjoyed this reflective piece from Math with Bad Drawings about determining whether a^b or b^a is larger. The final answer, involving the number e, was a complete surprise to me.

Short story: e is the unique number so that e^x > x^e for all positive x.

Powers Great and Small


Set a digital clock to display in 24-hour (military) time. Each day, it will show you 211 prime numbers starting with 00:02 (2 minutes after midnight) and ending with 23:57 (3 minutes before the next midnight.)

Oh, and 211 is also prime, so 02:11 would be one of the 211 prime times you observe each day.

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Source: https://www.facebook.com/PointlessMathFact/photos/a.959625970716963.1073741828.958620490817511/1427111183968437/?type=3&theater

A Classical Math Problem Gets Pulled Into the Modern World

I enjoyed this article about how the solution of a pure mathematics problem from a century ago is finding an unlikely application now: https://www.quantamagazine.org/a-classical-math-problem-gets-pulled-into-the-modern-world-20180523\

From the introductory paragraphs:

Long before robots could run or cars could drive themselves, mathematicians contemplated a simple mathematical question. They figured it out, then laid it to rest — with no way of knowing that the object of their mathematical curiosity would feature in machines of the far-off future.

The future is now here. As a result of new work by Amir Ali Ahmadi and Anirudha Majumdar of Princeton University, a classical problem from pure mathematics is poised to provide iron-clad proof that drone aircraft and autonomous cars won’t crash into trees or veer into oncoming traffic.

“You get a complete 100-percent-provable guarantee that your system” will be collision-avoidant, said Georgina Hall, a final-year graduate student at Princeton who has collaborated with Ahmadi on the work.

The guarantee comes from an unlikely place — a mathematical problem known as “sum of squares.” The problem was posed in 1900 by the great mathematician David Hilbert. He asked whether certain types of equations could always be expressed as a sum of two separate terms, each raised to the power of 2.

Mathematicians settled Hilbert’s question within a few decades. Then, almost 90 years later, computer scientists and engineers discovered that this mathematical property — whether an equation can be expressed as a sum of squares — helps answer many real-world problems they’d like to solve.

“What I do uses a lot of classical math from the 19th century combined with very new computational math,” said Ahmadi.

Greeting Cards for Scientists

Source: https://www.facebook.com/CTYJohnsHopkins/photos/a.323810509981/10150912351654982/?type=3&theater

Matrix Jokes

A lot more Matrix jokes can be found at https://mathwithbaddrawings.com/2018/03/07/matrix-jokes/

Adventures in Fine Hall: Princeton mathematics in the 1930s

I enjoyed reading this retrospective about the famous mathematicians at Princeton in the 1930s: https://paw.princeton.edu/article/adventures-fine-hall

From the opening two paragraphs:

The year was 1933. Members of the University’s mathematics department and the Institute for Advanced Study were celebrating the Institute’s opening with a party at the Princeton Inn, which is now Forbes College. “By chance,” an attendee later recalled, he entered just behind the Institute’s most famous faculty member, Albert Einstein. “As we walked across the lobby of the hotel, a Princetonian lady, of the Princetonian variety, strolled toward us. She was fairly tall and almost as wide, beautifully dressed, and she had an air of dignity. She strolled up to Einstein, reached out, put her hand up on Einstein’s head, ruffled his hair all over the place, and said, ‘I have always wanted to do that.’ ”

The source of this marvelous anecdote is Edward McShane, a distinguished mathematician, and the context is an intriguing series of interviews that the University conducted in the 1980s with people who had studied in the mathematics department in the 1930s. These interviews sought to capture the spirit of mathematics at Princeton during a golden age, a time when Einstein, Kurt Gödel, John von Neumann, and other analytical greats crossed paths on campus. In the process, the interviews captured something unexpected: a catalog of weirdness, a palette of colorful and off-kilter adventures that were going on in the background while the big papers were being written.


Source: https://www.facebook.com/MathWithBadDrawings/photos/a.822582787758549/1999420776741405/?type=3&theater

Trigonometry for the heavens

I enjoyed this article from the magazine Physics Today about the historical background behind three-dimensional spherical trigonometry: https://physicstoday.scitation.org/doi/10.1063/PT.3.3798

Codes and Ciphers Teaching Resources Website

Somehow I found this fun website with various teaching resources using different coding and decoding methods: http://www.cimt.org.uk/resources/codes/?fbclid=IwAR2yX_yDK0UAmLB2acIgbk15wJMy_QXFJSuKaQOj3q-SlrFkuuuxpsEXoyI

Engaging students: Arithmetic sequences

In my capstone class for future secondary math teachers, I ask my students to come up with ideas for engaging their students with different topics in the secondary mathematics curriculum. In other words, the point of the assignment was not to devise a full-blown lesson plan on this topic. Instead, I asked my students to think about three different ways of getting their students interested in the topic in the first place.

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission comes from my former student Danielle Pope. Her topic, from Precalculus: arithmetic sequences.

green lineHow can this topic be used in your students’ future courses in mathematics or science?

In the future, the topic of arithmetic sequences will be built upon by introducing another sequence, the geometric sequence. A geometric sequence is just a sequence of multiples instead of increasing by a constant. The next topic introduced will be finding the sum of a sequence of numbers. This will be introduced as a series. The summation symbol will also be introduced to kids and they will learn that new notation. Summations will bring along many formulas for finding the leading coefficient and will show up later in Calculus 2 classes when talking about convergence and divergence of series. Another one of the things that kids will always be doing with sequences and series is finding the general form of a given sequence or series. Through school, this idea will never change the sequence and series will just get harder to identify.
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What interesting things can you say about the people who contributed to the discovery and/or the development of this topic? (You might want to consult Math Through The Ages.)

An arithmetic sequence is a set of numbers that have a constant difference between each term. One of the main people that come up when researching these sequences is Carl Friedrich Gauss. Many math-loving people know him as the “Prince of mathematicians”. He is famous for coming up with the equations to solve the sum of an arithmetic sequence. This comes as no surprise that he came up with this formula. The surprising thing about this realization is that he made it at an age young enough to still be in grade school. Stories say that Gauss was asked to solve for the sum on the board in grade school and used the formula of M ( M + 1 ) / 2 to solve for the correct answer. This just goes to show that anyone can, in fact, contribute to the greater good of mathematics at any age.

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How have different cultures throughout time used this topic in their society?

One of the first civilizations that utilized sequences was the Egyptians. They used the sequence of multiples of 2 to do their multiplication. The basic sequence is 1, 2, 4, 8, 16, 32, … and we are trying to solve 24 x 13 with the process pictured below.

The process behind this is to write the multiple of 2 sequences down the left side of the paper until you reach the largest multiple of 2 without going over the second number being multiplied, in this case, 13. Once that is done set the first term on the right side equal to the first number being multiplied, in this case, 24. Next, multiply the right side by 4 until you get the same amount of terms on the left side. Lastly find the sum of numbers on the left that add to 13, which are 1, 4, and 8. Add the corresponding multiples from the side, 24 + 96 + 192 = 312. The right side sum of the corresponding numbers checked on the left gives the product of the original problem, i.e. 312. This trick is cool to show just on its own but it’s also cool because it uses something as simple as a specific list of numbers aka a sequence of numbers.