# Surface area of a cone

Areas related to cone are introduced with geogebra sketch.

### Objectives

Understand surface area

To calculate surface area of a cone

40 minutes.

### Prerequisites/Instructions, prior preparations, if any

Basics about cone, circle and pythogoras theorm should have been covered.

### Materials/ Resources needed

Digital: Laptop, geogebra file, projector and a pointer.

Geogebra file: Sector of a Cone , Surface area of a cone

### Process (How to do the activity)

The teacher after initial discussion on a cone and its properties can project the geogebra file and enable the understanding of derivation of formulae for surface area of a cone.

• Developmental Questions:
1. What is a solid shape ?
2. Define a cone ?
3. Give some examples of conical figures.
4. Name the parts of a cone.
5. What shape is its base.
6. After disection can you identify the shapes it is made of ?
7. Differentiate lateral surface area and total surface area.
8. What is the formula to find the area of a circle ?
9. Whatis the circumference of a circle ?
10. Differentiate between the slant height and vertical height of a cone.
11. How do we proceed to find the L.S.A. of the cone.
12. How do we find the total surface area of the cone.
• Evaluation:
1. What part of a circle is the lateral surface of a cone ?
• Question Corner:
1. What would be the formula to find the surface area of an ice-cream cone.
2. What is the frustum of a cone.