Altitude to the hypotenuse, step by step

Drop a perpendicular from the right angle onto the hypotenuse and the triangle splits into two more, each similar to the whole and to each other.

The question
1832hh =

Find the length of the altitude h.

The altitude as a geometric mean

big~left~right
same shapesame ratios
h² = p × q=18 × 32
576=24
  1. Dropping the altitude from the right angle onto the hypotenuse makes two smaller triangles. Each has a right angle, and each shares one of the original's acute angles — so all three triangles are similar.
  2. Similar means corresponding sides are in the same ratio. Writing that ratio down for the pair you want is the whole method; there is nothing to memorise beyond which pair.
  3. For the ALTITUDE the ratio pairs it with the two pieces: h/p = q/h, so h² = p × q.
  4. 576 under the root gives 24. "Geometric mean" is just the name for this: the middle term of a ratio that repeats.

How it works.

  1. 01

    Dropping the altitude from the right angle onto the hypotenuse makes two smaller triangles. Each has a right angle, and each shares one of the original's acute angles — so all three triangles are similar.

  2. 02

    Similar means corresponding sides are in the same ratio. Writing that ratio down for the pair you want is the whole method; there is nothing to memorise beyond which pair.

  3. 03

    For the ALTITUDE the ratio pairs it with the two pieces: h/p = q/h, so h² = p × q.

  4. 04

    576 under the root gives 24. "Geometric mean" is just the name for this: the middle term of a ratio that repeats.