# The Triangle of Abū’l-Wafā’

I found an interesting geometric statement in a paper of Glen Van Brummelen cited in the online MAA January 2020 issue of Convergence:

“For instance, Abū’l-Wafā’ describes how to embed an equilateral triangle in a square, as follows: extend the base GD by an equal distance to E. Draw a quarter circle with centre G and radius GB; draw a half circle with centre D and radius DE. The two arcs cross at Z. Then draw an arc with centre E and radius EZ downward, to H. If you draw AT = GH and connect B, H, and T, you will have formed the equilateral triangle.”

So the challenge is to prove this statement regarding yet another fascinating appearance of an equilateral triangle.

See the Triangle of Abū’l-Wafā’

# Abraham Lincoln, Technologist

I thought there was nothing new we could learn about Abraham Lincoln, but I see I was quite mistaken after reading Sidney Blumenthal’s article,  “Abraham Lincoln, Tech Entrepreneur”.

In the current oppressive anti-science climate it is important to look back at our history and see how integral scientific thinking was to our founding and development.  Not only were our Founding Fathers scientists, such as Jefferson and Franklin who with others founded the American Philosophical Society in 1743, but it turns out that President Abraham Lincoln could also lay claim to a scientific mind.  Blumenthal’s article describes in detail how Lincoln employed science to advance the development of our country.  You should read the entire article, but I am including some highlights.

# Root Difference

This is another problem from the 2020 Math Calendar.

“Find the difference between the highest and lowest roots of

f(x) = x3 – 54x2 + 969x – 5780”