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Pythagorean Theorem Calculator | Find Missing Side of a Right Triangle

Pythagorean Theorem Calculator

Calculate the length of any side of a right triangle using the Pythagorean theorem. Enter two known sides and find the missing side instantly.

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50,000+ Students

Pythagorean Theorem Formula

a² + b² = c²
Where ‘a’ and ‘b’ are the lengths of the two legs of the right triangle, and ‘c’ is the length of the hypotenuse (the side opposite the right angle).
a
b
c

Calculate Missing Side

Enter Known Values

Instructions

  1. Enter the lengths of any two sides of the right triangle.
  2. Leave the field empty for the side you want to calculate.
  3. Click the “Calculate” button to find the missing side.
  4. Use the “Reset” button to clear all fields and start over.

Note:

The hypotenuse (c) is always the longest side of a right triangle and is always opposite the right angle. If you’re calculating the hypotenuse, make sure it’s longer than both legs.

Calculating…

Calculation Results

Side a
Side b
Side c (Hypotenuse)
Perimeter
Area
Missing Side

Frequently Asked Questions

What is the Pythagorean Theorem?

The Pythagorean Theorem is a fundamental relation in Euclidean geometry among the three sides of a right triangle. It states that the square of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides. This can be written as the equation: a² + b² = c², where c represents the length of the hypotenuse and a and b the lengths of the triangle’s other two sides.

How do I use the Pythagorean Theorem to find a missing side?

To find a missing side using the Pythagorean Theorem: 1) Identify which sides you know and which side you need to find, 2) If you need to find the hypotenuse (c), use c = √(a² + b²), 3) If you need to find one of the legs (a or b), use a = √(c² – b²) or b = √(c² – a²), 4) Plug in the known values and calculate the result. Our calculator automates this process for you.

Can the Pythagorean Theorem be used for any triangle?

No, the Pythagorean Theorem only applies to right triangles (triangles with one 90-degree angle). For other types of triangles, you would need to use different methods such as the Law of Cosines or the Law of Sines to find missing sides or angles.

Who discovered the Pythagorean Theorem?

The theorem is named after the ancient Greek mathematician Pythagoras, who lived around 570-495 BCE. However, evidence suggests that the Babylonians and Indians knew about this relationship long before Pythagoras. While Pythagoras may have been the first to prove it, the theorem was likely known and used by various civilizations for practical purposes like construction and land surveying.

What are some real-world applications of the Pythagorean Theorem?

The Pythagorean Theorem has numerous practical applications: 1) Architecture and construction – for ensuring corners are square, 2) Navigation – for calculating distances, 3) Computer graphics – for calculating distances between points, 4) Surveying – for measuring land, 5) Physics – for resolving vector components, 6) Astronomy – for calculating distances between celestial bodies, and 7) Everyday life – for determining the shortest path between two points.

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