pardon the English

hi studying to become a software engineer and i found this book. which branch of math is used in that book?

i've already studied precalculus and I'm reading calculus and multivariable-calculus and I'm also writing small programs in c.

I really want to do more complicated math, algorithms and software engineering. but i don't even recognize what kind of math is used in that book.

which books should i read? where do i go from here?