Answer:
Logos(logical appeal)
Step-by-step explanation:
'Logos'(logical appeal) is one of the three rhetorical devices proposed by Aristotle to persuade readers, the other two are ethos(ethical appeal) and pathos(emotional appeal).
In the given case, Sonia is using 'logos' or the 'logical appeal' as she employs factual mathematical derivations to support her theorem. Since she substantiates her claims reasonably and persuades the audience logically instead of using her character(globally recognized), the rhetorical device is 'logos.'