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Last updated on August 5th, 2025

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Math Formula for the Hypotenuse

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In mathematics, the hypotenuse is the longest side of a right triangle, opposite the right angle. In this topic, we will learn the formula to calculate the hypotenuse using the Pythagorean theorem.

Math Formula for the Hypotenuse for UK Students
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List of Math Formulas for the Hypotenuse

The hypotenuse is calculated in a right triangle using the Pythagorean theorem. Let’s learn how to calculate the hypotenuse using different scenarios.

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Math Formula for the Hypotenuse

The hypotenuse of a right triangle can be calculated using the Pythagorean theorem, which states that the square of the hypotenuse (c) is equal to the sum of the squares of the other two sides (a and b):

 

Hypotenuse formula: ( c = {a2 + b2})

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Importance of the Hypotenuse Formula

The hypotenuse formula is crucial in geometry and real-life applications.

 

Here are some important uses of the hypotenuse formula: 

  • It is used to determine the length of the diagonal in rectangular and square shapes. 
     
  • It helps calculate distances and angles in various fields such as construction, navigation, and physics. 
     
  • By understanding the hypotenuse formula, students can grasp concepts like trigonometry and vector analysis.
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Tips and Tricks to Memorize the Hypotenuse Formula

Many students find math formulas tricky and confusing.

 

Here are some tips and tricks to master the hypotenuse formula: 

  • Remember the mnemonic "A squared plus B squared equals C squared" to recall the Pythagorean theorem. 
     
  • Visualize the formula with a right triangle diagram to better understand the relationship between sides. 
     
  • Practice problems using real-life examples, such as calculating the diagonal length of a TV screen.
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Real-Life Applications of the Hypotenuse Formula

The hypotenuse formula plays a significant role in real-life scenarios.

 

Here are some applications of the hypotenuse formula: 

  • In construction, to determine the length of a ladder needed to reach a certain height when placed at a specific distance from a wall. 
     
  • In navigation, to calculate the direct distance between two points on a map. 
     
  • In physics, to find the resultant vector when two perpendicular forces are applied to an object.
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Common Mistakes and How to Avoid Them While Using the Hypotenuse Formula

Students often make errors when calculating the hypotenuse. Here are some mistakes and ways to avoid them:

Mistake 1

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Mixing up the sides of the triangle

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Students sometimes confuse the hypotenuse with the other sides of the triangle.

 

Remember that the hypotenuse is always the side opposite the right angle and is the longest side of the triangle.

Mistake 2

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Incorrectly applying the Pythagorean theorem

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Errors occur when students misapply the formula.

 

Always ensure that you correctly square the lengths of the two shorter sides and sum them before taking the square root.

Mistake 3

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Forgetting to take the square root

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Students might forget to take the square root after computing the sum of the squares of the other two sides

 

. Always remember that the hypotenuse is the square root of this sum.

Mistake 4

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Using the formula for non-right triangles

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The hypotenuse formula only applies to right triangles.

 

Ensure the triangle has a right angle before using the Pythagorean theorem.

Mistake 5

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Calculation errors with square roots

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Errors can occur when calculating square roots.

 

Double-check with a calculator to ensure accuracy, especially with non-perfect squares.

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Examples of Problems Using the Hypotenuse Formula

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Problem 1

Calculate the hypotenuse of a right triangle with sides 3 and 4.

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The hypotenuse is 5.

Explanation

Using the formula  ( c = {a2 + b2}) where a = 3, b = 4:

( c = {32 + 42})

={9 + 16}

= {25}

= 5

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Problem 2

Find the hypotenuse if one side is 5 and the other is 12.

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The hypotenuse is 13.

Explanation

Using the formula ( c = {a2 + b2}),  where a = 5, b = 12:

( c = {52 + 122})

= {25 + 144}

= {169}

= 13 

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Problem 3

A triangle has a hypotenuse of 10 and one side of 6. Find the other side.

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The other side is 8.

Explanation

Using the formula ( c2 = a2 + b2 ), where c = 10 and a = 6:

( 102 = 62 + b2 )

( 100 = 36 + b2 )

( b2 = 64 )

( b = {64} = 8 ).

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Problem 4

Find the length of the hypotenuse when the sides are 8 and 15.

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The hypotenuse is 17.

Explanation

Using the formula ( c = {a2 + b2}) , where a = 8, b = 15:

( c = {82 + 152}) 

= {64 + 225}

= {289} = 17 ).

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FAQs on the Hypotenuse Formula

1.What is the hypotenuse formula?

The formula to find the hypotenuse is: \( c = \sqrt{a^2 + b^2} \), where a and b are the other two sides of the right triangle.

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2.Can the hypotenuse be shorter than the other sides?

No, the hypotenuse is always the longest side of a right triangle.

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3.Does the hypotenuse formula work for non-right triangles?

No, the hypotenuse formula only applies to right triangles.

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4.What is the hypotenuse of a 5, 12, 13 triangle?

The hypotenuse is 13, as it is the longest side.

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5.How do you find a missing side if you know the hypotenuse and one side?

Use the formula \( c^2 = a^2 + b^2 \) and solve for the missing side. Subtract the square of the known side from the square of the hypotenuse, then take the square root.

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Glossary for the Hypotenuse Formula

  • Hypotenuse: The longest side of a right triangle, opposite the right angle.

 

  • Right Triangle: A triangle with one angle measuring 90 degrees.

 

  • Pythagorean Theorem: A mathematical equation that relates the lengths of the sides of a right triangle: ( a2 + b2 = c2 ).

 

  • Square Root: A value that, when multiplied by itself, gives the original number.

 

  • Diagonal: A straight line connecting two non-adjacent corners of a polygon or polyhedron.
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Jaskaran Singh Saluja

About the Author

Jaskaran Singh Saluja is a math wizard with nearly three years of experience as a math teacher. His expertise is in algebra, so he can make algebra classes interesting by turning tricky equations into simple puzzles.

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Fun Fact

: He loves to play the quiz with kids through algebra to make kids love it.

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