An Easy But Impossible Probability Problem
I like looking a little deeper into problems; here we’ll find that although the problem is simple if you take it on its own terms, those terms are actually impossible. Does it matter?
Curiosity
What If: Inventing “Pseudo-Complex” Numbers
We’ll work through a textbook exercise that encourages students to discover what it’s like to invent a new number system, as well as why some ideas work but others do not. The topic: What would happen if we changed the definition of the imaginary unit i so that its square is 1 rather than -1?
How to Evaluate Trig Functions (By Hand?)
In discussing the value of radians, we introduced the idea that trig functions are easier to evaluate that way. That raises the question, how do you find the value of a trigonometric function without a calculator, and how do calculators themselves do it? Let’s look into that.
Squares, Roots, and Negative Numbers
(New questions of the week) Two recent questions (five days apart, from high school students in different countries) were about nearly the same thing, and fit nicely together: What do you get when you square a square root, or take the square root of a square, but don’t know the sign of the number ahead …
Experimenting with Triangles and Circles
(A new question of the week) I intended to fit three problems into last week’s post, but the third was too interesting to shorten, so I’m posting it separately. The problem itself is not hard, but in looking for a more direct solution, we extend it, discovering (through geometry software) more general facts, which lead …
Hilbert’s Cookie Jar: Little Kids, Big Ideas
(A new question of the week) I enjoy getting questions from young children, as we did here. It forces us to try to express big ideas in simple words (or at least help their parents or teachers do so). A frequent subject of those questions is infinity – they seem fascinated by this concept, perhaps …
A Challenging Geometry Problem
(A new problem of the week) We usually look here at problems or concepts that are relatively basic and generally applicable; that could give a wrong impression of the kinds of questions we get. Here I want to show a recent example of a discussion about a problem, related to a geometric figure called the …
Kids Ask About Even and Odd Numbers
(Archive Question of the Week) Although high school and up probably constitute the majority of our questions, I always enjoy answering younger children. For today’s look at the archives, I thought I’d look at two such questions, both from 1999, and very memorable. The first is almost certainly the youngest “patient” we’ve ever had, and …
Arrhenius Equation: Which Graph is Right?
(New Question of the Week) Occasionally we get questions challenging the correctness of a textbook problem, or of a test grade. And sometimes we get questions about mathematics used in sciences like physics or chemistry, which lead us to explore unfamiliar fields. The most interesting question this week is one of these. It is one …
A Sample of Ask Dr. Math, Part 2: Questions Outside of School
In the first post, I gave a small sampling of questions we’ve had from students, parents, and teachers, all related to school, and discussed how we like to deal with these. But we also get many questions with no direct relation to school. These may come from people who actually use math in their work …
A Sample of Ask Dr. Math, Part 2: Questions Outside of School Read More »