# Mathematical Dictionary - Letter H

HECTARE - Area unit (symbol: ha) equivalent to 10,000 square meters.

HEPTACORD - Instrument that has seven strings.

HEPTAEDRO - Polyhedron with seven faces. A heptagonal base pyramid is a heptahedron.

HEPTAGON - A 7-sided polygon. When the sides are equal the heptagon is regular. HEPTASSILLA - Name given to the word that has seven syllables.

HEXAEDRO - A rectangular prism that has six square faces. Each set of three edges is at a point called the vertex and two of these edges always form a right angle. The six faces are parallel two by two. The regular hexahedron is also called a cube.

HEXAGON - Greek word formed by hexa (six) and gono (angle). A 6-sided polygon. HEXAGRAM - Figure formed by two equal equilateral triangles with the same center, and arranged so that the sides of one are respectively parallel to the sides of the other. The hexagram for the Israelites is a symbolic figure (symbol of Solomon) and therefore plays an important role in Jewish decorative art.

HYPERBOLE - Conic where the difference between the distances to two fixed points on the axis (foci) is constant.

HYPOTENUSE - The longest side of a triangle. It is the side that opposes the right angle of a triangle and is related to the collets by the Pythagorean Theorem.

HISTOGRAM - set of rectangles that have the bases on the x axis and the area proportional to the class frequencies. Diagram consisting of rectangles or lines drawn from a baseline, where their position along that line represents the value or amplitude of one of the variables, and its height, the corresponding value of a second variable. HORIZONTAL - Line parallel to the horizon.

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