Suunnikas

Suunnikas is a term used in Finnish geometry to describe a four-sided planar figure. In many contexts it corresponds to what is commonly called a trapezoid in English, defined as a quadrilateral with at least one pair of parallel sides, known as the bases. In some Finnish texts the term is used specifically for the trapezoid with exactly one pair of parallel sides, while figures with two pairs of parallel sides are treated as parallelograms; terminology can vary by curriculum.

The bases of a suunnikas are parallel to each other, and the non-parallel sides are referred to as the legs. The interior angles of any quadrilateral, including a suunnikas, sum to 360 degrees. If the legs are equal in length, the figure is an isosceles suunnikas (isosceles trapezoid), and its base angles are equal. In a right suunnikas, one leg is perpendicular to the bases, producing a right angle with each base.

Key formulas include the area, which is the product of the average of the lengths of the two bases and the height (the perpendicular distance between the bases): Area = ((base1 + base2) / 2) × height. The diagonals generally differ in length, though they are equal in an isosceles suunnikas. Height may be found from given side lengths and angles or by constructing a perpendicular distance between the bases.

Suunnikas appears in various applications such as architectural design, land surveying, and geometry problems where base lengths and heights are used to compute areas and other measurements. Related figures include parallelograms and rectangles, as well as isosceles trapezoids.

See also: parallelogram, rectangle, trapezoid.