Figure 4-17.-Equilateral triangle on a given inscribedcircle: another method.circle. Draw AB parallel to the horizontal centerline of the circle and tangent to the circumference.Then use a 30 0/600 triangle to draw AC and BCat 60° to AB and tangent to the circle.Another method of accomplishing thisconstruction is shown in figure 4-17. Draw radiiat 30° to the horizontal center line of the circle,intersecting the circumference at C and B. Thereis a third point of intersection at A, so you nowhave three radii: OA, OB, and OC. Draw the sidesof the triangle at A, B, and C, tangent to thecircle and perpendicular to the relevant radius.RECTANGLE: GIVENLENGTH AND WIDTHTo construct a rectangle with a given lengthand width, draw a horizontal line AB, equal tothe given length. With a straightedge and triangle,erect perpendiculars from A and B, each equalto the given width. Connect the ends of theperpendiculars.SQUARE: GIVEN LENGTH OF SIDEYou can construct a square with a given lengthof side by the method described for constructinga rectangle. Another method is shown in figure4-18. With a T square, draw horizontal line ABequal to the given length of side. With a T squareand a 45° triangle, draw diagonals from A andB at 45° to AB. Erect perpendiculars fromAFigure 4-18.-Square with a given length of side.and B, intersecting the diagonals. Thenconnect the points of intersection.SQUARE: GIVENLENGTH OF DIAGONALFigure 4-19 shows a method of constructinga square with a given length of diagonal. Drawhorizontal line AB, equal to the given length ofthe diagonal. Locate O at the center of AB,and lay off CD through O, perpendicular to andFigure 4-19.-Square with a given length of diagonal.4-6
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