Draw a circle. Then, draw two lines coming from the slightly back-ish sides of the circle. Then, draw an arc connecting the lines at the bottom. I'm doing this off the top of my head. So, it might be wrong.
For cube, you can draw a regular hexagon and draw a line from every other vertice to the center of it.
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For cube, you can draw a regular hexagon and draw a line from every other vertice to the center of it.