# What is Frustum of Cone in Geometry?

Frustum of cone is a geometric shape that is formed when a cone is cut with a plane parallel to its base, resulting in two separate pieces. The lower piece is called the frustum, while the top piece is called the cone. The word “frustum” derives from the Latin word “frustrum”, meaning “a broken piece.” This geometric shape can be used to calculate the volume and surface area of a cone, as well as the angles of the side faces.

## Types of Cone Frustums

There are two main types of cone frustums: right cone frustums and oblique cone frustums. A right cone frustum is created when a cone is cut with a plane parallel to its base and perpendicular to its axis. An oblique cone frustum is created when a cone is cut with a plane parallel to its base, but not perpendicular to its axis.

## Formulas for Cone Frustums

The formulas for calculating the volume and surface area of cone frustums are different from the formulas for calculating the volume and surface area of regular cones. To calculate the volume of a cone frustum, use the formula V = (1/3)h(A+B+AB/C). To calculate the surface area of a cone frustum, use the formula SA = (h/3)(A+B+sqrt(AB)).

## Pyramid and Cone Frustums

Cone frustums are similar to pyramids in that they both have triangular faces and triangular bases. However, there are some key differences between them. A pyramid has a square base and four faces, while a cone frustum has a circular base and three faces. Additionally, the volume and surface area of pyramids can be calculated using the same formulas as regular cones.

## Conic Sections and Cone Frustums

Cone frustums are also related to conic sections, which are curves that are formed by intersecting a cone with a plane. Conic sections include circles, ellipses, parabolas, and hyperbolas. The intersection of a cone and a plane will always result in one of these four types of curves, depending on the angle of the plane.

## Practice Problems

1. Calculate the volume of a right cone frustum with a height of 10 cm, a base radius of 5 cm, and a top radius of 2 cm.

Answer: The volume of the right cone frustum is 50p cm^{3}.

2. Calculate the surface area of an oblique cone frustum with a height of 8 cm, a base radius of 4 cm, and a top radius of 2 cm.

Answer: The surface area of the oblique cone frustum is 56p cm^{2}.

3. A cone frustum is cut with a plane parallel to its base and perpendicular to its axis. What type of cone frustum is this?

Answer: This is a right cone frustum.

4. What type of curve is formed when a cone is intersected with a plane?

Answer: When a cone is intersected with a plane, one of the four types of conic sections is formed (circle, ellipse, parabola, or hyperbola).

5. Calculate the volume of a cone frustum with a height of 7 cm, a base radius of 4 cm, and a top radius of 2 cm.

Answer: The volume of the cone frustum is 28p cm^{3}.

6. Calculate the surface area of a right cone frustum with a height of 12 cm, a base radius of 6 cm, and a top radius of 3 cm.

Answer: The surface area of the right cone frustum is 96p cm^{2}.

## Summary

In this article, we discussed what a frustum of cone is in geometry, the different types of cone frustums, formulas for calculating the volume and surface area of cone frustums, how cone frustums are related to pyramids and conic sections, and practice problems with answers. Frustum of cone is a geometric shape that is formed when a cone is cut with a plane parallel to its base, resulting in two separate pieces. The lower piece is called the frustum, while the top piece is called the cone. Cone frustums are useful for calculating the volume and surface area of a cone, as well as the angles of the side faces.

## FAQ

### What is frustum in geometry?

In geometry, a frustum is a portion of a solid (normally a cone or pyramid) that has been cut off by two parallel planes. The resulting shape is generally a polyhedron.

### What are the properties of frustum of cone?

The properties of a frustum of a cone include its volume, surface area, and slant height. The base of a frustum of a cone can also be used to calculate the area of the original cone.

### Is frustum a geometric shape?

Yes, a frustum is a geometric shape, specifically a polyhedron.

### What is frustum of truncated cone?

A frustum of a truncated cone is a three-dimensional shape that has conical sides and a flat top and bottom. It is formed when a cone is cut off by a plane parallel to its base. The sides of the frustum are the conical parts of the cone that remain after the cutting plane has been passed through it.