===

To draw a circle in an isometric plane, you first have to draw the circumscribing square (which appears like a parallelogram in the isometric view). As shown in Figure 4.14 (a), it will be seen that the two angles:

• at A and C are acute angles (smaller than 90°); and
• at B and D are obtuse angles (bigger than 90°).

Follow the steps below:

Step 1:

Mark the midpoints of each side at E, F, G and H.

Figure 4.14 (a)

Step 2:

Join each of the obtuse angles (B and D in this case) to the two midpoints of the opposite sides as shown by the lines BH, BG, DE and DF in Figure 4.14(b). Where these lines intersect each other, we find the centre points J and K.

Figure 4.14 (b)

Step 3:

With centre J and radius H, drawn an arc touching sides AD and AB at H and E, respectively as shown in Figure 4.14 (c).

Do likewise with centre K giving an arc touching the other two sides at F and G.

Figure 4.14 (c )

Step 4:

With centre D and radius DF, draw another arc touching the sides BC and AB at F and E, respectively, thus joining the first two arcs as shown in Figure 4.14 (d). Repeat the process with centre B, which then completes the isometric circle.

Figure 4.14 (d )

Refer to the Student Portal for additional resources related to this module.

Print your own Isometric grid sheets from the Resource Centre.