Right triangle
Area and perimeter, with the formula worked through and a drawing to scale.
Result
- Area
- 6 sq ft
- = 6 sq ft · 0.557418 m²
- Perimeter
- 12 ft
- = 12 ft · 3.6576 m
- Hypotenuse c
- 5 ft
- Angle opposite a
- 36.8699°
- Angle opposite b
- 53.1301°
The working
Area: A = a × b ÷ 2
Perimeter: P = a + b + √(a² + b²)
A = a × b ÷ 2 = 3 × 4 ÷ 2 = 6 c = √(a² + b²) = √(3² + 4²) = 5 P = a + b + c = 12
Values in feet; areas in sq ft.
About the right triangle
The triangle behind every stair, roof and squaring job. The hypotenuse comes from Pythagoras — 3, 4, 5 is the builder's check for a square corner.
Every formula on this site is explained step by step in Learn: area and perimeter.
Other shapes
Square Rectangle Parallelogram Rhombus Trapezoid (trapezium) Kite Triangle — three sides Triangle — base and height Isosceles triangle Equilateral triangle Triangle — two sides and the angle between Circle Semicircle Quarter circle Sector (pie slice) Circular segment (arch) Ring (annulus) Ellipse (oval) Regular polygon (pentagon, hexagon, octagon…) L-shape Any polygon — by corner points