\fdO'^ - Old Forge Coal Mines

236 SURVEYING.
(622) 1st. A B in Fig. 61 is the given line 3 in. long.
At A and B erect perpendiculars A C and B D each 3 in.
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/
il> long. Join A D and B C.
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These lines will intersect at
some point E. The angles
EA ^and E B A are each 45°,
and the sides A E and E B
_
\ i f ^A^
must be equal, and the angle
A E B= 90°.
2d. A B \n Fig. 62 is the
g^ven line and c its middle
point. On A B describe the
Fig. 61. semicircle A E B. At r
erect a perpendicular to A B, cutting the arc A E B in-E.
Join A E and E B. The angle
A EB is 90°.
(623) See
and Fig. 237.
(624)
Art. 1181
See Art. 1187.
(625) (See Art. 1195
and Fig. 245.) Draw the line
A B, Fig. 63, 5 in. long, the length of the given side. At
A draw the indefinite line A C, making the angle B A C
equal to the given angle of 30°. On ^ Clay off ^ i? 1.5
in. long, the given difference between the other two sides of