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Right Triangle
Give the two legs of a right triangle and get the hypotenuse plus both acute angles. Built on the Pythagorean theorem and inverse tangent.
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💡 Good to know: Ancient builders made perfect right angles with a rope knotted into 3-4-5 segments — no protractor needed.
Worked example
Hypotenuse: 5 · Angle A°: 36.869898 · Angle B°: 53.130102
How it’s solved
Worked on the example above, step by step — follow along and you can do it on paper next time, no tool required.
- The Pythagorean theorem: in a right triangle the hypotenuse squared equals the sum of the squares of the two legs.
- Square each leg and add them
3² + 4² = 25 - Take the square root for the hypotenuse
√25 = 5 - Angle A = arctan(a ÷ b)
arctan(3 ÷ 4) = 36.869898°
Learn the method
Inputs
- Side a
3 - Side b
4
Frequently asked
What's the hypotenuse of a 3-4 triangle?
5 — a classic Pythagorean triple, with angles of about 36.87° and 53.13°.
Which angle is which?
Angle A is opposite side a; angle B is opposite side b. They always add to 90°.