# Surface area of a cone

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Areas related to cone are introduced with geogebra sketch.

### Objectives

Understand surface area

To calculate surface area of a cone

### Estimated Time

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

Download this geogebra file from this link.

Download this geogebra file from this link.

### 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:

- What is a solid shape ?
- Define a cone ?
- Give some examples of conical figures.
- Name the parts of a cone.
- What shape is its base.
- After disection can you identify the shapes it is made of ?
- Differentiate lateral surface area and total surface area.
- What is the formula to find the area of a circle ?
- Whatis the circumference of a circle ?
- Differentiate between the slant height and vertical height of a cone.
- How do we proceed to find the L.S.A. of the cone.
- How do we find the total surface area of the cone.

- Evaluation:

- What part of a circle is the lateral surface of a cone ?

- Question Corner:

- What would be the formula to find the surface area of an ice-cream cone.
- What is the frustum of a cone.