Circle with a segment as its radius

Set stroke width to 2r

Duplicate the ellipse and turn theminto upper and lower arcs each by dragging the circular handle with the CTRL-key pressed.

Stroke to path

Break nodes

Do it in situ.

Romove unnecessary(red) arcs

Toroid coil wrapped around a torusHow to draw torus and toroid in Inkscape

A B

C

A B

A

C

Stroke style: round cap

Draw the projection of the axial circle(locus of the center of generating circle)

To draw the projection ofthe generating circle,first draw the projectionof its diameters touchingthe bounding square.

1. Draw the inner and outer equators of the torus as the loci of the ends of the radial diameter.2. Then draw the (projection of) the radiusof the torus that cuts the equators.3. Copy the projection of the axial diameter, and paste it so that its midpoint agrees with the intersection of the radius and equators of the torus.4. Copy the projection of the radial diameter on the toric radius and paste itso that its midpoint agrees with the end-points of the projection of the axial diameters.

Let me call the diameters of thegenerating circle as axial and radial,respectively if its parallel or perpendicular to the axis of revolution.

The projected axial and radial diametersare conjugate diameters of the projectionof the image of generating circle, which is an ellipse.

Using the theorems of Apollonius that theconjugate diameters of a given ellipse makea parallelogram of constant area, and the factthe major axis is equal to the diameter of the generating circle, we can construct its minor axis.

Once the major and minor axes are found, the nexttask is to find the angle to rotate the ellipse so thatit touches the projection of the bounding square.1. Draw a circle of radius equal to the half length ofthe projection of radial diameter and centered at the intersection of the projected toric radius and theprojected axial circle.2. Find the intersection of the circle drawn and the ellipse tobe rotated.3. Rotate the ellipse so that the intersection meets the end of the projected axial diameter.

}{projectedaxial diameter

width ofboundingparallelogram

} diameterof generatingcircle

generating circleaxis of revolution

projection of the image of the generating circle