# The Flying Colours Maths Blog: Latest posts

## The Mathematical Ninja and the twenty-sixths

The Mathematical Ninja played an implausible trick shot, not only removing himself from a cleverly-plotted snooker, but potting a red his student had presumed safe and setting himself up on the black. Again. “One!” he said, brightly, and put some chalk on the end of his cue. The student sighed.

## Wrong, But Useful: Episode 35

In this month’s Wrong, But Useful, Dave and Colin discuss: Colin gets his plug for Cracking Mathematics in early Colin is upset by a missing apostrophe Dave teases us with the number of the podcast and asks about the kinds of things it’s reasonable to expect students to know, and

## A lovely trigonometric identity

When I was researching the recent Mathematical Ninja piece for Relatively Prime, I stumbled on something at MathWorld1 I’d never noticed before: if $t = \tan(x)$, then: $\tan(2x) = \frac{2t}{1 – t^2}$ $\tan(3x) = \frac{3t – t^3}{1 – 3t^2}$ $\tan(4x) = \frac{4t – 4t^3}{1 – 6t^2 + t^4}$ \$\tan(5x) =