Finding a Missing Side
Ages 11–15Difficulty adapts to you
Finding a Missing Side
When you know the hypotenuse and one other side, rearrange the formula to find the missing side: a² = c² − b².
Your goals
- ✓You can use the theorem to find a shorter side when you know the hypotenuse.
- ✓You can use leg, hypotenuse correctly.
- ✓You can square the hypotenuse, subtract the other squared side, then take the principal square root.
Words to know
- leg:
- One of the two sides that form the right angle.
- hypotenuse:
- The side opposite the right angle.
Examples
- 1If c = 13 and b = 5: a² = 169 − 25 = 144, so a = 12.
- 2If c = 10 and a = 6: b² = 100 − 36 = 64, so b = 8.
Check these
- • Do not add the squares when finding a shorter side.
- • Keep every number, symbol, label, and unit in its correct place.
- • Show enough working to check how you reached your answer.
Helpful habits
- • Read the whole question before choosing what to do.
- • Show one clear step at a time and check each step.
- • If you are stuck, draw a model, try smaller numbers, or revisit the example.
Now try your own
Create your own finding a missing side example, solve it, and explain how you checked it.
Professor Wise Owl
Wisdom & Understanding“Take your time — wisdom comes from understanding, not rushing!”