Semiperimeter
The semiperimeter of a geometric figure is one half of the perimeter, or , where is the total perimeter of a figure. It is typically denoted . In a triangle, it has uses in formulas for the lengths relating the excenters and incenters.
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Applications
The semiperimeter has many uses in geometric formulas. Perhaps the simplest is , where is the area of a triangle and is the triangle's inradius (that is, the radius of the circle inscribed in the triangle).
Two other well-known examples of formulas involving the semiperimeter are Heron's formula and Brahmagupta's formula.