Full resolution (JPEG) - On this page / på denna sida - Geometry - Problems in geometrical drawings
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
PROBLEMS IN GEOMETRICAL DRAWING. 185
angle but an angle of 90° can simultaneously touch three points
in the circumference when two of these points are in the point
of intersection with the diameter and
the circumference and the third one
anywhere on the circumference of the
half circle. The pattern maker is mak^
ing practical use of this geometrical
principle, when he by a common car-
penter’s square is trying the correctness
of a semi-circular core box, as shown
in Fig. 5.
Draw a line parallel to a
given line. (See Fig. 6).
Given line a b. The required
line x y.
Solution
:
Describe with the compass a—
from the line a b, the arcs 1 and
2 ; draw line x y, touching these arcs
x—=-
Fig. 6
To divide a given angle into two
equal angles.
The given angle, a b c, is divid-
ed by the line b d.
Solution:
With b as center and any radius,
as b 1, describe the arc 1 to 2. With
1 and 2 as centers and any suitable
radius, describe arcs cutting each
other at d. Draw line b d, which
will divide the angle into two equal parts.
To draw an angle equal to a given angle.
Given angle a b c. Construct
angle xy z.
With b as center and any radius,
as b 1, describe the arc 1 to 2.
UsingjK as center and without alter-
ing the compass, describe the arc /,
intersecting y z. Measuring the
distance from 2 to 1 on the given
angle, transfer this measure to the " 2
arc /, through the point of intersection. Draw the line y x,
and this angle will be equal to the first angle.
Note.—Angles are usually measured by a tool called a pro-
tractor, looking somewhat like Fig. 9 or 10, usually made from
metal, and supplied by dealers in draughting instruments. A
<< prev. page << föreg. sida << >> nästa sida >> next page >>
