CalcCalculatrice de Triangle Rectangle
Dernière mise à jour: 2026-05-09
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| Leg A | Leg B | Hypotenuse | |
|---|---|---|---|
| Caso basico | 1.2 | 1.6 | 0.4 |
| Caso tipico | 2.1 | 2.8 | 0.7 |
| Caso medio | 3.0 | 4.0 | 1.0 |
| Caso avanzado | 4.5 | 6.0 | 1.5 |
| Caso extremo | 7.5 | 10.0 | 2.5 |
Right Triangle Calculator: Pythagorean theorem and trigonometry
A right triangle has a 90° angle and is the foundation of trigonometry. This calculator uses the Pythagorean theorem and sine, cosine and tangent functions to find unknown sides and angles.
Pythagorean theorem and trigonometry
In a right triangle with legs a, b and hypotenuse c:
- Pythagoras: a² + b² = c²
- Sine: sin(θ) = opposite / hypotenuse
- Cosine: cos(θ) = adjacent / hypotenuse
- Tangent: tan(θ) = opposite / adjacent
Knowing two sides or one side and one angle, you can determine all remaining values of the triangle.
Example 1: finding the hypotenuse
Problem: A right triangle has legs a = 3 cm and b = 4 cm.
- Apply Pythagoras:
- c² = 3² + 4² = 9 + 16 = 25.
- Hypotenuse:
- c = √25 = 5 cm.
Answer: c = 5 cm (the famous 3-4-5 triangle).
Example 2: finding an angle
Problem: A triangle has opposite leg = 5 cm and adjacent leg = 12 cm.
- Hypotenuse:
- c = √(5² + 12²) = √(25 + 144) = √169 = 13 cm.
- Angle θ:
- tan(θ) = 5/12 ≈ 0.4167.
- θ = arctan(0.4167) ≈ 22.62°.
Answer: c = 13 cm, θ ≈ 22.62°.
Utilisations courantes
- Computing inaccessible distances and heights in surveying.
- Determining the incline of ramps, stairs and roofs.
- Solving navigation and orientation problems.
- Analyzing forces and components in physics and engineering.
- Computing diagonal distances on screens and monitors.
- Foundation of applied trigonometry in architecture.
Common mistakes with right triangles
- Confusing the opposite leg with the adjacent leg relative to the reference angle.
- Using degrees instead of radians (or vice versa) on the calculator.
- Applying Pythagoras to triangles that are not right triangles.
- Forgetting that the hypotenuse is always the longest side.
Conseil pro
Memorize common Pythagorean triples (3-4-5, 5-12-13, 8-15-17) and special angles (30°-60°-90° and 45°-45°-90°). They will save you calculations in many practical problems.
No. The Pythagorean theorem only applies to right triangles. For other triangles, use the law of cosines.
It is a mnemonic: Sin = Opposite/Hypotenuse, Cos = Adjacent/Hypotenuse, Tan = Opposite/Adjacent.
Not directly. For general triangles you need the law of sines or the law of cosines.
It depends on what you have and what you need. If you have opposite and hypotenuse, use sine. If adjacent and hypotenuse, use cosine. If both legs, use tangent.