. The Decorator's assistant. from e, withE A as radius, describe the arc a d ; then thepoint D will be the centre of the polygonrequired. PROBLEM XXVIII, To find the angles at the centre and circum-ference of a given polygon. Divide 360 by the number of sides of thegiven polygon, and the quotient will be theangle at the centre; and this angle being sub-tracted from 180, the difference will be theangle at the circumference required. Accord-ing to this method, the following table hasbeen calculated, showing the angles at thecentres and circumferences of regular poly-gons, from three to twelve si
. The Decorator's assistant. from e, withE A as radius, describe the arc a d ; then thepoint D will be the centre of the polygonrequired. PROBLEM XXVIII, To find the angles at the centre and circum-ference of a given polygon. Divide 360 by the number of sides of thegiven polygon, and the quotient will be theangle at the centre; and this angle being sub-tracted from 180, the difference will be theangle at the circumference required. Accord-ing to this method, the following table hasbeen calculated, showing the angles at thecentres and circumferences of regular poly-gons, from three to twelve sides inclusive. Names, Sides. Angles atthe Centre. Angles at theCircumference. deg. min. deg. min. Trigon 3 120 0 60 0 Tetragon ... 4 90 0 90 0 5 72 0 108 0 6 60 0 120 0 Heptagon 7 51 25 5-7 128 34 2-7 Octagon ... 8 45 0 135 0 9 40 0 140 0 Decagon ... 10 36 0 144 0 Undecagon 11 32 43 7-n 147 16 4-11 Dodecagon 12 30 0 150 0 PROBLEM XXIX. To make a triangle similar and equal to agiven THE DECORATOR S ASSISTANT. 127
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