What is the point of a thesis defense presentation? Context: math master's thesis.
I get that I need to show up and be able to have a discussion and answer questions, etc. That's all fine and good.
But in my uni, 70 % of the thesis defence consist of my own presentation. Then maybe 25 % of the time is alloted for questions, and 5 % for grading.
What is the point of that 70 %?
Am I supposed to just re-summarize the entire thesis?
The point of the thesis presentation is so the examiners can see if you actually did the work in the thesis or not.
It's quite easy to paraphrase content from e.g. publications, to ask one's supervisor for assistance tackling technical aspects of the work. So, by seeing you present the work and asking you some questions about the content, the examiners can assess whether you actually understand what you're talking/writing about.
Think of it as a presentation followed by an oral examination on the content. Some tips (I am not a mathematician but hopefully these are generally applicable):

Be clear about what problem your work is addressing.
Be clear about why that problem is actually worth addressing.
Make sure you give due credit to the relevant literature (e.g. with citations).
Don't spend more than 1/3 of the presentation on the points above.
Focus on what your contributions were to solving the problem described above.

Hope this helps.