Mathematics surely starts with counting and basic arithmetic; perhaps some understanding of repetition and regular intervals comes next, but geometry was surely not far behind. It was surely where mathematics first got formalised and axiomatised, at least; and several ancient civilisations recognised the significance of some of its consequences. In this part of my web-site, I explore some of the basic results of classical geometry, particularly those involving pictorial proofs (presented using SVG images, for the most part). More algrebraic treatments of geometry remain elsewhere.

- Conventional markings and simple results
- Isosceles triangles (with two edges of equal length) and some properties of circles
- The three centres of a triangle
- A nice elegant curve that results from a whole bunch of straight lines.
- Pythagoras's theorem and its diverse proofs
- How to take the square root of an area.
- Some (more) properties of quadrilaterals with their corners on a circle
- Basic trigonometry, angles and their units
- Rectangles whose diagonals trisect corners
- How to construct a regular pentagon

I'm a bit haphazard about adding to and maintaining this area.

- A quick overview of area formulae.
- A game of challenges using circle and straight line construction.
- Good approximations to π.