I'm a first year physics and astrophysics double major. My schedule has me taking Differential Equations next year and Linear Algebra the following semester(or vice versa, I haven't asked my advisor which to take first). After that there are no required math courses to complete my degree. What are some math classes I should take beyond linear algebra/differential equations? Would a math minor supplement my degree well or is it unnecessary? And if there are no truly necessary math classes which ones are useful/interesting? I'm definitely interested in taking more so any advice is much appreciated!