Algebra and geometry you can move.
Maths you can take hold of. Drag the picture, watch what changes, and notice what refuses to.
A rectangle cut corner to corner into two triangles. This one can be dragged about, which needs JavaScript switched on.
It keeps happeningThe diagonal always cuts the rectangle into two equal halves. Make it very wide. Make it very flat. Try to break it.
Notice, then nameEvery lesson goes the same way. You move something yourself first, and only then is it written down as a rule.
Where to startChapter one is yours with a free account — the whole chapter, not a sample. A subscription opens the other six.What a subscription opens