Mathematics · Glossary
What is Pythagorean Theorem?
Quick definition
In a right triangle, the square of the hypotenuse equals the sum of the squares of the two legs: a² + b² = c².
Full explanation
The Pythagorean Theorem states that in a right triangle (one with a 90° angle), the relationship between the three sides is a² + b² = c², where c is the hypotenuse (longest side, opposite the right angle) and a, b are the two legs. Attributed to the Greek mathematician Pythagoras (~570–495 BC), though Babylonians knew it earlier. The theorem has thousands of proofs and is the foundation of trigonometry, distance formulas, and 3D geometry. It only works for Euclidean (flat) space — not on spheres or curved surfaces. Generalizations exist: the Law of Cosines for non-right triangles, and the metric tensor in general relativity.
Related calculators
Calculators that use or explain Pythagorean Theorem.
Related terms
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Standard Deviation
A measure of how spread out numbers are from their mean. Low = consistent, high = volatile.
P-Value
The probability of observing results at least as extreme as those observed, assuming the null hypothesis is true.
Mean (Average)
The sum of values divided by the count. The most common type of "average." Sensitive to outliers.
Median
The middle value in a sorted list. Half the values are above, half below. Robust to outliers.
Logarithm
The exponent to which a base must be raised to produce a given number. log(100) = 2 means 10² = 100.
Exponent
A number that indicates how many times a base is multiplied by itself. 2³ = 2×2×2 = 8.
Last reviewed: June 15, 2026 • Category: Mathematics