This geometry book from 1847 (!!) uses “colored diagrams and symbols instead of letters for the greater ease of learners.”
For example, consider this right-angled triangle…
… and two ways of stating facts about it.
The old way (quoting from the book):
- The angle BAC, together with the angles BCA and ABC are equal to two right angles, or twice the angle ABC.
- The angle CAB added to the angle ACB will be equal to the angle ABC.
- The angle ABC is greater than either of the angles BAC or BCA.
And the new way:
I loved geometry in high school, but it was despite the drab textbooks. Why isn’t this the standard way geometry is taught everywhere?
(via Public Domain Review)