Octagon eight lines of reflective symmetry and rotational symmetry of order 8. A regular octagon is represented by the Schläfli symbol {8}. The internal angle at each vertex of a regular octagon is 135° (formula_1 radians). The central angle is 45° (formula_2 radians). The area of a regular octagon of side length "a" is given by In terms of the circumradius "R", the area is In terms of the apothem "r" (see also inscribed figure), the area is These last two coefficients bracket the value of pi, the area of the unit circle. The area can also be expressed as where
Angle gauge needs to know the limiting distance for a tree. The PRF using a 10 BAF angle gauge is for every inch of tree diameter. Therefore, 20 inches × 2.75 ft/inch = . This means that a tree must be over away from the center of the plot using a BAF 10 angle gauge to be out of the plot. Angle gauge An angle gauge is a tool used by foresters to determine which trees to measure when using a variable radius plot design in forest inventory. Using this tool a forester can quickly measure the trees that are in or