slightly longer than AB. Use a T square and a 45°triangle to draw AF and EB at 45° to AB and CD,Connect AE and FB.SQUARE IN A GIVENCIRCUMSCRIBED CIRCLEFigure 4-20 shows a method of drawing asquare in a given circumscribed circle. Draw thediameters AB and CD at right angles to eachother, and connect the points where the diametersintersect the circumference of the circle.SQUARE CIRCUMSCRIBED ON AGIVEN INSCRIBED CIRCLEFigure 4-21 shows a method of circumscribinga square on a given inscribed circle, Drawdiameters AB and CD at right angles to eachother. Then draw each side of the square tangentto the point where a diameter intersects thecircumference of the circle and perpendicular tothe diameter.ANY REGULAR POLYGON IN AGIVEN CIRCUMSCRIBED CIRCLEYou can construct any regular polygon in agiven circumscribed circle by trial and error witha drafting compass or dividers as shown in figure4-22. To draw a nine-sided regular polygon in thecircle shown, divide the circumference by trial anderror with a compass or dividers into nine equalsegments, and connect the points of intersection.To get a trial spread for a compass or dividers,divide the central angle subtended by the entirecircle (360) by the number of sides of the polygon,in this case, by nine. Then, lay off the centralangle quotient from the center of the circle to thecircumference with a protractor.ANY REGULAR POLYGON ON AGIVEN INSCRIBED CIRCLEThe same method (dividing the circumferenceinto equal segments) can be used to construct aregular polygon on a given inscribed circle. In thiscase, however, instead of connecting the pointsof intersection on the circumference, you draweach side tangent to the circumference andFigure 4-20.-Square in a given circumscribed circle.Figure 4-21.-Square on a given inscribed circle.Figure 4-22.-Regular polygon in a given circumscribedcircle.4-7
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