When run the angle on the right hand side which should be displayed in the third part of the question was not being displayed. On leaving and going back in again it was displayed. All OK in Chrome. Now the question, nor any others, will not load in IE - this issue put in editor.
As Christian found, fix for the lack of display is to add a line of code after the last display wanted which displays outside the canvas - only for IE purposes of course. Not closed as yet.
Not quite sure if editor or numbas issue.
See https://numbas-editor.mas.ncl.ac.uk/question/515/triangles/
When run the angle on the right hand side which should be displayed in the third part of the question was not being displayed. On leaving and going back in again it was displayed. All OK in Chrome. Now the question, nor any others, will not load in IE - this issue put in editor.