This is not a textbook, but a guide and handbook for mathematics. It
treats just about every subject you are likely to have had in an undergraduate
class in mathematics for engineers, but with less explanations and no homework.
In addition it contains enough material about many branches of mathematics
so that you will at least be able to find out what area of mathematics
you need to solve a problem, and gives you at least some information about
some basic and even advanced techniques in the field.

You should not let yourself be deterred by the fact that it has some
clearly outdated information about computers. If you have sold your calculus
textbook, and sometimes think that was a bad idea, it is worth considering
buying this book, which costs about $ 60. I know that twenty years ago
(almost) every engineering student in Germany owned the German translation
of this book. If you want to take a look at it, you can do so in my office.

2. Numerical Recipes in C: The Art of Scientific Computing, by William H. Press, Saul A. Teukolsky, William T. Vetterling, Brian P. Flannery, Hardcover, 994 pages, 2nd ed. (1992), The Press Syndicate of the University of Cambridge, ISBN: 0521431085

This book addresses the methods available to numerically solve a great
variety of different problems, with explanations about how and why these
methods work and what can go wrong when one is using them. It also contains
ready-made code in C, which you can also get on a CD, for these problems.
Versions in other programming languages are available.