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TRANSFER OF AN ANGLE There is a geometric construction for laying off, on another part of the same drawing or on a different drawing, an angle Figure 410.Transferring an angle. equal in size to one that is already drawn. This procedure, called transferring an angle, is shown in figure 410. Here, the draftsman desired to lay off from O´ a line that would make an angle with B´O´ equal to angle BOA. To do this, draw an arc through OB and OA, with O as a center, as shown in figure 410, view A. Then, draw an arc of the same radius from B´O´, with O´ as a center, as shown in figure 410, view B. Next, measure the length of the chord of the arc between OB and OA and lay off the same length on the arc from B´O´, as shown in figure 410, view C. A line drawn from O´ through A´ makes an angle with B´O´ equal to angle BOA, as shown in figure 410, view D. BISECTION OF AN ANGLE To bisect an angle means to divide it in half. If you know the size of the angle, you can bisect it by simply dividing the size by 2 and laying off the result with a protractor. Geometric construction for bisecting an angle is shown in figure 411, To bisect the angle AOB, first lay off equal intervals from O on OA and OB. With the ends of these intervals as centers, strike intersecting arcs of equal radius at P. Draw a line from O through the point of intersection of the arcs, P. The line OP bisects angle AOB. PLANE FIGURES This section explains how to construct certain plane figures, such as the triangle, rectangle, square, and regular polygon. You must understand the geometrical construction of plane figures because they appear in engineering drawings. Figure 411.Bisecting an angle. Figure 412.Constructing a triangle with three sides given. TRIANGLE: THREE SIDES GIVEN To draw a triangle with three sides given, first draw a straight line AB, equal in length to one of the given sides (fig. 412). With A as a center, strike an arc with a radius equal to the given length of the second side. With B as a center, strike an intersecting arc with a radius equal to the length of the third side. Draw lines from A and B to the point of intersection of the arcs. 

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