Inserting a matrix in Mathematica Online

Questions
,
1

How do I insert a matrix in Mathematica Online? The documentation says it should be under the Insert menu, but it is not there in my Online session.

Also, is there a good place that describes the Online interface for someone who is used to the desktop interface?

Thanks.

2

In Mathematica a matrix is a list of lists so to enter a 3 x 3 identity matrix type:
{{1,0,0},{0,1,0},{0,0,1}} or more simply IdentityMatrix[3].
To get a dot product type:

{{1,0,0},{0,1,0},{0,0,1}}.{{a,b,c},{d,e,f},{g,h,i}}

or

Dot[{{1,0,0},{0,1,0},{0,0,1}},{{a,b,c},{d,e,f},{g,h,i}}]

In the Desktop version of Mathematica, keyboard entry or the Basic Math Assistant allows you to enter a matrix of the size you require with empty place holders but this doesn’t seem to be possible with Mathematica Online.