A triangle is cannot be the shape of a cross section of this cylinder
Depending on the angle of the cut, a cylinder's cross-section can have a variety of shapes, but usually consists of rectangles, parallelograms, and circles.
Triangles are one shape that cannot be a cylinder's cross-section. The cross-sectional shapes of a cylinder are typically more rounded or curved, such as circles, ellipses, or some forms of rectangles.
A triangle does not match these shapes. The geometric characteristics of a cylinder would not be consistent or fit by a triangular cross-section.