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The Baudhayana-Pythagoras Theorem

A square on every side

Draw a triangle with sides 3, 4 and 5. Build a square outwards on each side.

A 3, 4, 5 triangle.
Step 1 of 4
  1. A 3, 4, 5 triangle.
  2. A square on the side of 3 holds 3 × 3 = 9 tiles.
  3. A square on the side of 4 holds 4 × 4 = 16 tiles.
  4. A square on the side of 5 holds 5 × 5 = 25 tiles.

Rule: a square on side s holds s × s unit tiles. A unit tile is a square of side 1. A square of side 3 has 3 rows of 3 tiles. The tile count is the square's area. To square a number is to multiply it by itself.

A right-angled triangle has one square corner, which is 90°. Squares can be built on any triangle's sides, not just right-angled ones. A triangle with sides 4, 5 and 6 has no square corner. Its three sides still have squares of 16, 25 and 36 tiles.

Drag the slider. Count the tiles inside.

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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

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