DOI Page / Citation link:
https://doi.org/10.11588/diglit.62828#0088
’Of the Line of Sines on the Senior.
A Sine is a right line drawn from one end of an arch
perpendicularly upon the diameter drawn from the other end
of that arch, as the perpendicular line 90, drawn from the
diameter BA, Fig. 12, Plate II. is the line of the arch BD;
and fo like wife all the other perpendicular lines, as 1,2, 3, 4, 5,
See. on the line B A, are fines of fo many different portions of
the arch B D A.
The line of Sines on the feftor, which Fig. 13 is intended
to reprefent, is marked r j nigh 90.90, with two brafs centers,
one on each limb of the inftrument. The feveral divifions on
this line, marked 10, 20, 30, &c. anfwer to thefe perpendicular
lines 1, 2, 3,4, 3, &c. on the line B A, Fig. 12, and the different
fituations of thofe perpendicular lines are found by dividing
the arch D A into nine equal divifions. Perpendiculars being
then drawn from each refpeTive divifion on the circumference
of the circle to the diameter A B, they are of courfe denomi-
nated fines of 10, 20,30 degrees, and fo on.
To draw an Oval by the Senior.
Firft, Draw a circle that will comprehend the longed dia-
meter of the oval you wifh to defcribe, as the circle BDA,
Fig. 12. Divide the quadrant DA into nine equal parts.
Second,
A Sine is a right line drawn from one end of an arch
perpendicularly upon the diameter drawn from the other end
of that arch, as the perpendicular line 90, drawn from the
diameter BA, Fig. 12, Plate II. is the line of the arch BD;
and fo like wife all the other perpendicular lines, as 1,2, 3, 4, 5,
See. on the line B A, are fines of fo many different portions of
the arch B D A.
The line of Sines on the feftor, which Fig. 13 is intended
to reprefent, is marked r j nigh 90.90, with two brafs centers,
one on each limb of the inftrument. The feveral divifions on
this line, marked 10, 20, 30, &c. anfwer to thefe perpendicular
lines 1, 2, 3,4, 3, &c. on the line B A, Fig. 12, and the different
fituations of thofe perpendicular lines are found by dividing
the arch D A into nine equal divifions. Perpendiculars being
then drawn from each refpeTive divifion on the circumference
of the circle to the diameter A B, they are of courfe denomi-
nated fines of 10, 20,30 degrees, and fo on.
To draw an Oval by the Senior.
Firft, Draw a circle that will comprehend the longed dia-
meter of the oval you wifh to defcribe, as the circle BDA,
Fig. 12. Divide the quadrant DA into nine equal parts.
Second,