What were the hardest subjects in maths when you started physics as a bachelor student?

[Maclaurinssadism]

I'm a recent bachelor student into physics and I am really struggling with these type of maths. Especially infinite series and its tests, the Integral Test and etc. If it was easy for you, what type of books did you use or methods?

 

[FactChecker]

A lot of undergraduate math subjects have a small set of tricks. If you learn 3, you get a C, learn 5 and you get a B, learn 7 and you get an A. You must survive that, but often those tricks do not give you great insight. Keep your eyes open for the exceptions: power series and complex numbers, linear equations, fourier series, etc. Those are the subjects that you really want to take to heart. The subject of differential equations has a dozen tricks, but the basics are really fundamental. You can tell that if there is an entire math class on a subject, then you will see a bit of it in the early classes that you should pay special attention to.
For practice in solving problems, I always recommend the Schaum's Outline series.

 

[jedishrfu]

The one trick among many that i still recall was integrating y first before x in a double integral.

The prof mentioned it in passing and then on the surprise quiz he had such an integral impossible to integrate starting with x first but a piece of cake when starting with y.

Another was from Linear Algebra, in adding and subtracting rows in a matrix to get a 1 value in a column over dividing the selected row by the inverse of the column number.

More recently, I learned that Euler's formula could be used to derive the sin/cos relationships for adding and subtracting angles.