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
Firste the circle is, as you see, A.B.C.D, and his centre E, his
diameter is A.D, Then is ther a line drawẽ from A. to B, and so
forth vnto F, which is without the circle: and an other line
also frome B. to D, whiche maketh two cantles of the whole
circle. The greater cantle is D.A.B, and the lesser cantle is
B.C.D, In whiche lesser cantle also there are two lines that
make an angle, the one line is B.C, and the other line is C.D.
Now to showe the difference of an angle in a cantle, and an
angle of a cantle, first for an example I take the greter cãtle
B.A.D, in which is but one angle made, and that is the angle by
A, which is made of a line A.B, and the line A.D, And this angle
is therfore called an angle in a cantle. But now the same cantle
hathe two other angles, which be called the angles of that
cantle, so the twoo angles made of the righte line D.B, and the
arche line D.A.B, are the twoo angles of this cantle, whereof
the one is by D, and the other is by B. Wher you must remẽbre,
that the ãgle by D. is made of the right line B.D, and the arche
line D.A. And this angle is diuided by an other right line
A.E.D, which in this case must be omitted as no line. Also the
ãgle by B. is made of the right line D.B, and of the arch line
.B.A, & although it be deuided with ij. other right lines, of
w^{ch} the one is the right line B.A, & thother the right line
B.E, yet in this case they ar not to be cõsidered. And by this
may you perceaue also which be the angles of the lesser cantle,
the first of thẽ is made of y^e right line B.D, & of y^e arch
line B.C, the secõd is made of the right line .D.B, & of the
arch line D.C. Then ar ther ij. other lines, w^{ch} deuide those
ij. corners, y^t is the line B.C, & the line C.D, w^{ch} ij.
lines do meet in the poynte C, and there make an angle, whiche
is called an angle made in that lesser cantle, but yet is not
any angle of that cantle. And so haue you heard the difference
betweene an angle in a cantle, and an angle of a cantle. And in
lyke sorte shall you iudg of the ãgle made in a semicircle,
whiche is distinct frõ the angles of the semicircle. For in this
figure, the angles of the semicircle are those angles which be
by A. and D, and be made of the right line A.D, beeyng the
diameter, and of the halfe circumference of the circle, but by
the angle made in the semicircle is that angle by B, whiche is
made of the righte line A.B, and that other right line B.D,
whiche as they mete in the circumference, and make an angle, so
they ende with their other extremities at the endes of the
diameter. These thynges premised, now saie I touchyng the
Theoreme, that euerye angle that is made in a semicircle, is a
right angle, and if it be made in any cãtle of a circle, thẽ
must it neds be other a blũt ãgle, or els a sharpe angle, and in
no wise a righte angle. For if the cantle wherein the angle is
made, be greater then the halfe circle, then is that angle a
sharpe angle. And generally the greater the cãtle is, the lesser
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