Skip to content
Exit presentation

The Baudhayana-Pythagoras Theorem

Start here

A gate has a bar cut on a slant, corner to corner. That bar is called a diagonal. How long should it be?

Figure 1 — one diagonal bar makes two right-angled triangles.

This is Part II, Chapter 2, The Baudhayana-Pythagoras Theorem.

Two people give the rule its name. Baudhayana was from India. Pythagoras was from Greece.

What you will learn

  • The long side — across from the square corner, the 90° corner.
  • A square on every side — a real square, drawn and counted.
  • The one addition — the two small squares' tiles equal the big square's.
  • Only at 90° — change the angle and the totals stop matching.
  • Finding the long side — from the two short ones.
  • Finding a short side — when the long one is already known.
  • Testing a triangle — three lengths, and no protractor.
  • Out in the field — a ladder, a gate, a field, a charpai.
  • Corner to corner — the square on the diagonal has twice the area.
  • A decimal long side — find two decimals it lies between.
  • One triple, many — scale a triple and it stays a triple.
  • A hidden depth — a bent stem shows a pond's depth.

Each lesson has a lab, apart from the checkpoint, summary and quiz. Move the triangle yourself and watch the squares change.

Jump to lesson

This track

  1. 0 Start here
  2. 1 Naming the sides
  3. 2 A square on every side
  4. 3 The two smaller squares together
  5. 4 Only at a right angle
  6. 5 Finding the long side
  7. 6 Finding a shorter side
  8. 7 Testing a triangle without a protractor
  9. 8 Where it is used
  10. 9 Corner to corner of a square
  11. 10 The long side as a decimal
  12. 11 One triple makes many
  13. 12 The hidden depth of a pond
  14. 13 Checkpoint: roots, triples and a pond
  15. 14 The big picture
  16. 15 Track quiz

Other tracks