# Browsing category geometry

## How to think about co-ordinate geometry (Part III: Circles, tangents and so on)

This is the third and final part of the how to think about co-ordinate geometry series. Due to a failure of calendar-reading, I appreciate this is going out a few days after the C1 and C2 exams, but hey-ho. If you're relying on this blog for your revision tips, you

## How to think about co-ordinate geometry (Part II: curves, tangents and normals)

This is part two of a three-part series about co-ordinate geometry. In part I last week, I went into tedious detail about the equation of a line. This week, I’m going to take it a bit further and go into curves. Next week, you get to see circles. So, what

## How to think about co-ordinate geometry (Part I: the equation of a line)

Pretty much every C1 student I’ve ever worked with has said the same thing: I don’t get the big questions at the end of the paper. The ones with the curves and the equation of a line and the tangents and the turning points — what’s that all about? So,

## Completing the square – the easy way

-or- matching coefficients for fun and profit I bluffed my way through completing the square at A-level. I guessed, dropped minus signs, and dropped marks all the way. It was only once I started teaching it that I figured out completing the square. Let me share it with you. Completing

## What is a circle? (and how do you answer C2 questions about it?)

A conjecture both deep and profound Needs a proof that the circle is round. In a paper by Erdős Written in Kurdish A counter-example is found. One of my favourite questions to ask students is "what's a circle?" because I get to play "so that means this is a circle!"