Re-cip′i-an′gle.
An instrument (
a) with two legs and a graduated arc, used by military engineers for measuring and laying off angles of fortifications.
The legs are attached at one end by a double-headed screw, which forms the axis.
The center of the protractor is applied at the reentering angle of the instrument, and its graduated margin shows the angle of divergence of the legs.
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Recipiangles. |
Another form (
b) of the
recipiangle, called the
parallelogrammatic, has two links connecting the legs and meeting at the center
f. The length between the points
a d and
a c is exactly equal to the distances
d f and
c f, so that when the legs are brought into line, the point
f coincides with the point
a. The center of the protractor is exactly over the point
f, which also bisects the angle of the instrument at all adjustments.
The marginal graduation of the protractor permits the angle subtended thereby to be read.
The protractor is hinged at
g, so that it may be lifted and stand perpendicular to the plane of the instrument.
The instrument is adapted for taking salient or reentering angles.