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.
i86 PROBLEMS IN GEOMETRICAL DRAWING.
protractor may also be constructed on paper and used for
measuring angles, but it should then always be made on as
large a scale as convenient.
Fig. 10
Fig. 9
To draw a protractor with a division of 5°. (See Fig. 10).
Construct an angle of exactly 90 degrees, divide the arc into
nine equal parts, then each part is 10c
; divide each part into
two equal parts and each is 5°.
Prove that the sum of the three angles in a triangle consists
of 180°. (See Fig. 11).
Solution
:
In the triangle a b c, extend
the base line to i. Draw the line
o fi,
parallel to the side a b,
thereby the angle g will be equal
to the angle d, and the angle h
/ must be equal to angle c. The
6 angle/is one angle in the triangle
and / + g + h = 1S0°, therefore
/ + d + c must also be 180°.
To draw on a given base line a triangle having angles 90°,
30° and 60°. (See Fig. 12).
Given line a b, required triangle is a, c, b.
Solution
:
Extend the line a b to twice its
length, to the point e. With e and b as
centers strike arcs intersecting each
other and erect the perpendicular a c.
With b as center and any radius as /,
draw the arc / ?n. With / as center
and with the same radius, describe arc
intersecting at m. From b through
point of intersection at w, draw line b
intersecting the perpendicular at c.
This will complete the triangle.
Fig.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
