Final answer:
The cross section formed when a cylinder is cut by a plane parallel to its base is a circle, as the points on the cut are equidistant from the axis, making the cross section circular.
Step-by-step explanation:
When a cylinder is cut by a plane parallel to its base, the shape of the cross section formed is a circle. This occurs because the cutting plane is parallel to the base, which means every point on the cut surface is equidistant from the cylinder's central axis, forming a perfect circle.
Cylinders, being three-dimensional objects with parallel sides, have a simple relationship between their volume and cross-sectional area, where the volume (V) is the cross-sectional area times the height (V = Ah). In context to conic sections, if a cylinder is seen as a cone with a top of the same size as its base, cutting it with a plane parallel to the base will always result in circular cross-sections, as opposed to other conic sections like ellipses, parabolas, and hyperbolas that result from different angles of cutting planes on cones.