Thank yoy Mauno.
As usual: you gave a very simple and practical solution.
In administration - plugins - filters - mathjax
I inserted tex2jax: {displayMath: [ ['\\[','\\]'] ], inlineMath: [ ['$$','$$'],['\\(','\\)'] ] },
so that I got: (see attachment)
At first sight: this works perfectly for me.
Thanks to everyone who helped think of a solution.
Best regards, and gratefull mathematical taughts
Patrick
