The Path-Way to Knowledg, Containing the First Principles of GeometrieRecord, Robert
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The Path-Way to Knowledg, Containing the First Principles of Geometrie
Record, Robert
Geometry -- Early works to 1800
_The .liij. Theoreme._
If a pointe bee marked without a circle, and from it diuerse
lines drawen crosse the circle, to the circumference on the
other side, so that one of them passe by the centre, then
that line whiche passeth by the centre shall be the loongest
of them all that crosse the circle. And of the other lines
those are longest, that be nexte vnto it that passeth by the
centre. And those ar shortest, that be farthest distant from
it. But among those partes of those lines, whiche ende in
the outewarde circumference, that is most shortest, whiche
is parte of the line that passeth by the centre, and
amongeste the othere eche, of thẽ, the nerer they are vnto
it, the shorter they are, and the farther from it, the
longer they be. And amongest them all there can not be more
then .ij. of any one lẽgth, and they two muste be on the two
contrarie sides of the shortest line.
_Example._
[Illustration]
Take the circle to be A.B.C, and the point assigned without it
to be D. Now say I, that if there be drawen sundrie lines from
D, and crosse the circle, endyng in the circumference on the
cõtrary side, as here you see, D.A, D.E, D.F, and D.B, then of
all these lines the longest must needes be D.A, which goeth by
the centre of the circle, and the nexte vnto it, that is D.E, is
the longest amongest the rest. And contrarie waies, D.B, is the
shorteste, because it is farthest distaunt from D.A. And so maie
you iudge of D.F, because it is nerer vnto D.A, then is D.B,
therefore is it longer then D.B. And likewaies because it is
farther of from D.A, then is D.E, therfore is it shorter then
D.E. Now for those partes of the lines whiche bee withoute the
circle (as you see) D.C, is the shortest. because it is the
parte of that line which passeth by the centre, And D.K, is next
to it in distance, and therefore also in shortnes, so D.G, is
farthest from it in distance, and therfore is the longest of
them. Now D.H, beyng nerer then D.G, is also shorter then it,
and beynge farther of, then D.K, is longer then it. So that for
this parte of the theoreme (as I think) you do plainly perceaue
the truthe thereof, so the residue hathe no difficulte. For
seing that the nearer any line is to D.C, (which ioyneth with
the diameter) the shorter it is and the farther of from it, the
longer it is. And seyng two lynes can not be of like distaunce
beinge bothe on one side, therefore if they shal be of one
lengthe, and consequently of one distaunce, they must needes bee
on contrary sides of the saide line D.C. And so appeareth the
meaning of the whole Theoreme.
Public-domain text, read in full here on John Shaqi.
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