1
00:00:00,000 --> 00:00:04,000
Start with a right triangle: sides 3, 4, 5.

2
00:00:04,000 --> 00:00:08,000
Build a square on each shorter side.

3
00:00:08,000 --> 00:00:12,000
Compare their areas with the longest-side square.

4
00:00:12,000 --> 00:00:16,000
9 + 16 = 25. The right angle matters.