The Path-Way to Knowledg, Containing the First Principles of GeometrieRecord, Robert
Science
The Path-Way to Knowledg, Containing the First Principles of Geometrie
Record, Robert
Geometry -- Early works to 1800
Deuide firste the circle as you did in the last conclusion into
fiue equall portions, and draw fiue semidiameters in the circle.
Then make fiue touche lines, in suche sorte that euery touche
line make two right angles with one of the semidiameters. And
those fiue touche lines will make a cinkangle of equall sides
and equall angles.
[Illustration]
_Example._
A.B.C.D.E. is the circle appointed, which is deuided into fiue
equal partes. And vnto euery prycke is drawẽ a semidiameter, as
you see. Then doo I make a touche line in the pricke B, whiche
is F.G, making ij. right angles with the semidiameter B, and
lyke waies on C. is made G.H, on D. standeth H.K, and on E, is
set K.L, so that of those .v. touche lynes are made the .v.
sides of a cinkeangle, accordyng to the conclusion.
An other waie.
Another waie also maie you drawe a cinkeangle aboute a circle,
drawyng first a cinkeangle in the circle (whiche is an easie
thyng to doe, by the doctrine of the .xxxvij. conclusion) and
then drawing .v. touche lines whiche shall be iuste paralleles
to the .v. sides of the cinkeangle in the circle, forseeyng that
one of them do not crosse ouerthwarte an other and then haue you
done. The exaumple of this (because it is easie) I leaue to your
owne exercise.
THE XL. CONCLVSION.
To make a circle in any appointed cinkeangle of equall sides
and equall corners.
Drawe a plumbe line from any one corner of the cinkeangle, vnto
the middle of the side that lieth iuste against that angle. And
do likewaies in drawyng an other line from some other corner, to
the middle of the side that lieth against that corner also. And
those two lines wyll meete in crosse in the pricke of their
crossyng, shall you iudge the centre of the circle to be.
Therfore set one foote of the compas in that pricke, and extend
the other to the end of the line that toucheth the middle of one
side, whiche you liste, and so drawe a circle. And it shall be
iustly made in the cinkeangle, according to the conclusion.
_Example._
The cinkeangle assigned is A.B.C.D.E, in whiche I muste make a
circle, wherefore I draw a right line from the one angle (as
from B,) to the middle of the contrary side (whiche is E. D,)
and that middle pricke is F. Then lykewaies from an other corner
(as from E) I drawe a right line to the middle of the side that
lieth against it (whiche is B.C.) and that pricke is G. Nowe
because that these two lines do crosse in H, I saie that H. is
the centre of the circle, whiche I would make. Therfore I set
one foote of the compasse in H, and extend the other foote vnto
G, or F. (whiche are the endes of the lynes that lighte in the
middle of the side of that cinkeangle) and so make I the circle
in the cinkangle, right as the cõclusion meaneth.
[Illustration]
THE XLI. CONCLVSION
To make a circle about any assigned cinkeangle of equall
sides, and equall corners.
Public-domain text, read in full here on John Shaqi.
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