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Missing side (c)
About This Calculator
The Pythagorean theorem relates the sides of a right triangle: a² + b² = c², where c is the hypotenuse (the side opposite the right angle).
Solving
- Hypotenuse: c = √(a² + b²)
- Leg: a = √(c² − b²) — the hypotenuse must be longer than the leg.
This is the backbone of trigonometry, construction, and navigation.
Frequently Asked Questions
Which side is the hypotenuse?
The hypotenuse is always the longest side and sits opposite the 90° right angle. The two shorter sides are the legs (a and b).
Can I use this for non-right triangles?
No — it only works for right triangles. For other triangles use the Law of Cosines: c² = a² + b² − 2ab·cos(C).