Ask HN: What math to study for a high schooler with 1 month and calculus base?

We will finish the Anton Calculus 'Brief Edition' textbook with 1 month left in the year. So after integrals we'll have covered Infinite series as well, to give you a sense of what math knowledge we'll be at.

I was wondering if any HNers have advice for what math topics I could independently study with my teacher in the remaining time, that also won't be repeated knowledge for college. e.g. I do not want to study vectors since I will be taking linear algebra later anyhow.

Thank you for your time and kind help!