659
OF ENGINEERING FORMULÆ,
Table of Polygons.
S » Side of polygon. __
11 = Radius of circumscribed circle.
r = Radius of inscribed circle. __
A = Angle formed by the intersection of tlio
sides.
Name. Sides. A. Area = 82 X s = nx S = rX
Trigon .. 3 60° •4330 1-732 3-4641
Pentagon .. 5 108° 1-7205 1-1755 1-4536
Hexagon .. 6 12(1° 2-5980 1-0000 1-1547
Octagon .. 8 135° 4*8284 •7653 0-8284
Decagon .. 10 144° 7-6942 •6180 •6498
Area of any regular polygon = Radius of in-
scribed circle X j number of sides X length of one
side.
Table of Polyhedrons.
Name. No. of Sides. R = SX r = SX A = S*X jo = S3X
Tetrahedron 4 O'«124 •2041 1-7320 ) 0-1178
Hexahedron 6 •8660 •5C00 6’ObOO 1 1-0OÜÜ
Octahedron. 8 •7071 •4082 3'4641 1 -4714
Dodecahedron 12 1'4012 1-1135 20'6458 j 7'6631
Icosahedron 20 •9510 •7558 8'6602 2’1817
S = Length of linear edge of a side.
R = Radius of circumscribed circle.
r = Radius of inscribed circle.
A = Area of polyhedron.
C = Cube contents of polyhedron.
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