1, a circle is round as long as its cross section is parallel to the bottom. If cut diagonally, the cross section is elliptical. Go home and find a radish to cut. It's spicy, sweet, juicy and crisp. Eat radish in winter and ginger in summer without a doctor's prescription.

2. Rectangular. If the front of the view is square, it can be determined that the shaded part is rectangular.

3, isosceles triangle, the cone is cut from top to bottom, no matter how it is cut, it is an isosceles triangle section, because the length of the two waists is always equal to the root sign (bottom radius? +Cone height? )