**Ex 12.3**

This video goes through how to find the area of a composite shape. This is: Q5e in Ex 12.3 |
This video goes through how to solve another composite shape problem. This is Q5f |
This video explains how to use CAS to calculate areas both as a decimal approximation and in exact form. |

**Ex 12.4**

This video explains where the formula for the Perimeter of a Sector comes from |
This video goes through calculating the Perimeter of a Sector, Ex 12.4, Q4a |
This video expains how to calculate the Area of a Sector, Ex 12.4, Q4a |

**Ex 12.5**

This video explains how to draw the net of a rectangular prism (also called a cuboid), which makes it easier to understand what the total surface area of a rectangular prism is.This video goes through an example of how to calculate the total surface area of a triangular prism. |
This video gives you a little more information about the nets of a rectangular prism. |
This video goes through an example of how to calculate the total surface area of a rectangular prism (cuboid). |