Question

The diagram shows a cone and its axis of rotation. If a plane passes through the axis of rotation, which type of cross section will be formed?
A: a circle

B: an isosceles triangle

C: a parabola

D: an oval

Answer 1

Isosceles triangle.

B

Answer 2

Answer:  The answer is (B). An isosceles triangle.

Step-by-step explanation:  In the given figure, a cone and its axis of rotation is shown. We are to select the type of cross-section that will be formed if the plane passes through the axis of rotation.

See the attached figure, if a plane passes through the axis of rotation of the cone, then the resultant cross-section will be a triangle with one vertex as the vertex of the cone, i.e., A. And also, the two sides of the triangle through the vertex A will be equal.

The cross-section is also shown in the attached figure and it will be an isosceles triangle ABC, where AB = AC.

Thus, the correct option is  (B) an isosceles triangle.