面積の公式 - Math.net

Area formula home / geometry / area and perimeter / area formula Area formula The area of a two dimensional shape or geometric figure is the space contained within its perimeter. Area formulas of common shapes The exact area of many common shapes can be calculated using well-defined formulas. Circle The area of a circle with radius r is: A = πr 2 Triangle The area of a triangle with base, b, and height, h, is: If the side lengths of the triangle are given, the area can be found using: where a, b, and c are side lengths, and Equilateral triangle The area of an equilateral triangle with side length, s, is: Square The area of a square with side, s, is: A = s 2 Rectangle The area of a rectangle with length, l, and width, w, is: A = lw Parallelogram The area of a parallelogram with base, b, and height, h, is: A = bh Trapezoid The area of a trapezoid with bases, b 1 and b 2 , and height, h, is: Kite and Rhombus The area of a kite , or rhombus , with diagonal length d 1 and d 2 is: Regular hexagon The area of a regular hexagon with side length s is: Regular pentagon The area of a regular pentagon with side length s is: Regular octagon The area of a regular octagon with side length s is: Ellipse The area of an ellipse with semi-major axis, a, and semi-minor axis, b, is: A = πab Area of a composite figure Many geometric figures are made up of two or more common figures, and their areas can be calculated using a combination of the area formulas above. These types of geometric figures are referred to as composite figures. Example: Find the area of the composite figure below to the nearest tenth. The figure is composed of an equilateral triangle, a rectangle, and a semi-circle (half of a circle). Using the formula for the area of an equilateral triangle and side length 10: The length and width of the rectangle are 10 in and 4 in respectively, so its area is A = 10×4 = 40 The area of the semi-circle is one-half the area of a circle. The semi-circle has a radius of 5 and its area can be found by halving the area formula of a circle: The total area of the composite figure is the sum of all its parts: A = 86.6 + 40 + 39.3 = 122.6 Area and perimeter Area formula Area of a hexagon Area of a parallelogram Area of a rectangle Area of a rhombus Area of a square Area of a trapezoid Perimeter Perimeter of a rectangle about us | sitemap | terms | privacy © 2026 math.net