### Video Transcript

Here is the parallelogram π΄π΅πΆπ·. Part a) On the diagram, mark the angle π΅πΆπ· with the letter π₯.

One of the mathematical conventions for labelling angles is to use three letters. The middle letter is always the letter that describes the vertex at which the angle is situated. The first and last letters give you a path to follow. Letβs see what this looks like.

The path we want to follow starts at π΅ and then goes to πΆ then back out to π· again. The angle π΅πΆπ· sits at the vertex πΆ. So itβs this one labelled π₯.

Here is the square-based pyramid πππ
ππ. Part b) Shade the face ππ
π.

In geometry, the word βfaceβ is used to describe one of the flat surfaces on a 3D shape. In this shape, there are triangular faces and a square face. The face ππ
π is the triangle enclosed by these three letters.

Like we did with the angles, we start at π, go to π
, then from π
to π. And since it is a triangle, back again from π to π. We can then shade the face ππ
π, as shown.

Part c) How many faces does a square-based pyramid have?

We said that the pyramid has some triangular faces and a square face. The square face sits at the base of the pyramid; thatβs the first face. Since the square has four sides and the triangular faces come off of each of these sides, there must be four triangular faces. One plus four is five; thatβs a total of five faces.