The ARC tool is located in the middle section of the sketch toolbar.
Either POLYGON tool can make regular figures between 3 and 50 sides
On the sketch created in MyFirstPart:
Note: The tool actually creates an Circumscribed Polygon which is defined as a polygon placed outside a circle so that all the vertices of the polygon lie outside the circumference of the circle and all lines are tangent to the circle.
or
Note: The tool actually creates an Inscribed Polygon which is defined as a polygon placed inside a circle so that all the vertices of the polygon lie on the circumference of the circle
or
*A circumscribed figure is a shape drawn outside another shape. For a polygon to be inscribed inside a circle, all of its corners, also known as vertices, must touch the circle. If any vertex fails to touch the circle, then it's not an inscribed shape.