Don't feel pressured to do an 'arts' take on maths if you don't want to.
It's my bug bear with the EPQ that it's done in such a way that it almost makes it seem bold or unusual to research a science subject, when in reality people write dissertations on maths and science subjects all the time at universities.
I did an EPQ on a maths subject and found that instead of doing the usual essay, I could produce an 'artefact' and then write a 'popular press' article/summary about it for a non-specialist audience (the exam board was AQA).
It's definitely possible to score highly taking this approach.