Ellipse Construction, ContinuedConcentricIn the concentric diameters method of ellipse construction, you use the majordiametersmethodand minor axes as diameters for concentric circles on a common horizontaland vertical axis intersecting at right angles. By drawing a diagonal acrossboth circles and plotting subsequent points, you can construct an ellipse.To construct an ellipse using the concentric diameters method, use this table:Step1234567ActionDraw horizontal (AB) and vertical (CD) axes that intersect at rightangles (0).Using the length of the major and minor axes as diameters, lay outtwo concentric circles with 0 as a common center.Draw a diagonal (XX) at any common angle through thecircumferences of both circles passing through 0. Every diagonaldrawn provides you with four points along the circumference of theellipse.From points X, draw lines XS parallel to CD and perpendicular toAB .Where XX intersects the smaller circle, draw HE parallel to ABand perpendicular to CD.Draw as many diagonals you feel necessary to adequately definethe ellipse.Lightly sketch the ellipse through the points. Darken the outline ofthe ellipse using french curves.Continued on next page2-50
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