Using an iPhone/iPad to present mathematics in MS Teams by sharing the screen

If you would like to use an iPhone/iPad to present something within Teams (eg an iPad with an Apple Pen to present mathematical notation to a MS Teams meeting/class/tutorial/lecture), then this can be done as follows:

In preparation go to the Settings App
Open the Control Centre.
Click the green "Plus" next to "Screen Recording" so that it moves into the INCLUDE section (unless you had done this before)
Install Microsoft Teams on your iPhone/iPad from the Apple App Store
Log in as normal, ie specify your email address first and then sign in with your single sign-on account.
Join a meeting as you would normally do on your desktop/laptop - it works best if you use iPhone/iPad as a secondary device as your main device will still be streaming the video feed of you.
Once in a meeting, open Teams on the iPhone/iPad, you will see an "In progress: Meeting" on the top and can click "Join" to join it. Alternatively you could join from calendar or chat channel if that is how you did it initially.
Once you joined the meeting you can now move to your presentation/annotation app, eg "Notes".
Once in that open control center (swipe down on top right corner) and long press (Microsoft call it "firmly") the round "recording" button.
Select "Microsoft Teams" and hit "Start Broadcast"
After a countdown it will start broadcasting your screen.
To stop screen sharing you can toggle the recording button in the Control Center again and also hang up in Teams on the iPad.