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Geometry is easier than you think. Plane geometry is based on concepts that on their own are extremely simple; if you can draw a line, you can do geometry. So, whether you need some help with homework or you'd just like to understand geometry a bit more, here's a guide to understanding it.

Firstly, lets go right back to basics. Draw two lines on a sheet of paper; one going vertically down the left hand side and the other horizontally along the bottom. With a ruler, put a small mark every centimetre on both lines. Already, you have in front of you the basis of all geometry. With geometry, using nothing more than these two lines you can describe any location on the page.

For example, we can describe the exact position of a dot on the page (technically now a two-dimensional 'plane') with just two numbers. These numbers are called co-ordinates ("co" means "together", since we always need both numbers together), and are written in brackets like this: (4, 7).

This simply tells us where our dot is in relation to our lines. To find our dot, you could put a pen at the place where the two lines cross, called the 'origin', and follow the numbers like instructions. (4, 7) therefore means we move the pen 4 units to the right, then 7 units towards the top of the page. Simple! We just located a dot, technically called a 'point', using just two numbers. In fact, we could even use negative numbers to describe a point that is to the left of the vertical line or below the horizontal line. For example, (5, -7) means 'five units right and seven units down'.

The two lines we drew are called 'axes' - a horizontal axis and a vertical axis. To make it quicker to write down, we can give them a single letter instead. The standard convention is to call the horizontal axis 'x' and the vertical one 'y'. If you're wondering where 'z' has got to, we'll mention this later.

Now we have a system for describing locations in the form of points we can describe more complex objects. A point is known as zero-dimensional because it has no size; it is just the name given to a place precisely at the co-ordinates we want. If we draw two points and join them up we now have a one-dimensional line segment. It's only dimension is length (of course, the pencil line has width so we can see it but in theory it has no width).

We can also define lines by an equation that tells us what the co-ordinates will be. For example, we know that (4, 7) means x=4 and y=7, meaning 'four along and seven up'. Now I can describe

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