Solve the whole triangle from any two parts.
Enter any two of the two legs, the hypotenuse, or an acute angle. The calculator solves every remaining side and angle, the area and perimeter, the trig ratios, and draws the triangle to scale.
What you know
What the numbers mean
Triangle scorecard
Trig ratios for angle A
SOHCAHTOA: sine, cosine and tangent are ratios of the sides seen from angle A. Side a is opposite, side b is adjacent, c is the hypotenuse.
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Right triangles, explained
Right Triangle Properties
A right triangle has one 90° angle. The side opposite the right angle is the hypotenuse, the longest side. The other two sides are called legs. The Pythagorean theorem (a² + b² = c²) relates the three sides and is one of the most fundamental relationships in mathematics.
Calculating Angles in a Right Triangle
Since one angle is always 90°, the other two must sum to 90° (complementary). Use trigonometry: angle A = arctan(a/b) and angle B = arctan(b/a). Alternatively, angle A = arcsin(a/c) or arccos(b/c). All methods give the same result.
Common Right Triangle Ratios
Special right triangles have memorized ratios. The 3-4-5 triangle (and multiples like 6-8-10, 5-12-13) are Pythagorean triples. The 45-45-90 triangle has sides in ratio 1:1:√2. The 30-60-90 triangle has sides in ratio 1:√3:2. These shortcuts speed up calculations.
Applications of Right Triangles
Right triangles are used in construction (roof pitch), navigation (bearing calculations), surveying (measuring heights), physics (force components), and computer graphics (distance calculations). Trigonometric functions (sine, cosine, tangent) are all defined using right triangles.
Common questions
What is the hypotenuse?
The hypotenuse is the longest side of a right triangle, located opposite the 90° angle. Its length is c = √(a² + b²). For a 3-4-5 triangle, the hypotenuse is 5.
What are Pythagorean triples?
Pythagorean triples are sets of three positive integers where a² + b² = c². Common examples: (3,4,5), (5,12,13), (8,15,17), (7,24,25). Any multiple of a triple is also a triple (e.g., 6,8,10).
How do I find a missing leg?
If you know the hypotenuse (c) and one leg (a), the other leg is b = √(c² - a²). This calculator requires both legs and computes the hypotenuse.
How is the area of a right triangle calculated?
Area = ½ × a × b, where a and b are the two legs. The legs serve as the base and height since they are perpendicular to each other.
For learning and planning only. Rounding is applied for display, so recomputed values may differ slightly from the exact result.