SCOPE: Basic mathematics, entry-level quantitative mathematics, transitory period between quantitative/applied mathematics and pure mathematics, introduction into pure mathematics. Follow the path, taking from the "smorgasboard" whatever you need.
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>CATEGORY 0 "Pre-Math: Grade School Mathematics":
Elementary Algebra – H. S. Hall & S. R. Knight
Higher Algebra – H. S. Hall & S. R. Knight
Geometry: Book I. Planimetry – A. P. Kiselev
Geometry: Book II. Stereometry – A. P. Kiselev
Plane Trigonometry – S. L. Loney
Statistics - David Freedman
Note: What an ideal "grade school math" curriculum should look like. Probably best to serve as a reference material for those less skilled in quantitative mathematics.
>CATEGORY 0.5 "Pre-Math: Grade School Review":
Algebra – I. M. Gelfand
Pre-Calculus - Carl Stitz & Jeff Zeager
Note: Best review for the most bang for your buck. Successful completion of both books should adequately prepare you for entry-level mathematics.
>CATEGORY 0.75 "Pre-Math: Competition-Style Problems"
Challenging Problems in Algebra – Dover Publications
Challenging Problems in Geometry – Dover Publications
Challenging Problems in Probability – Dover Publications
Note: Will help ensure that foundations are strong, but otherwise wholly optional and most likely not needed.
>CATEGORY 1 "Pre-Math: Entry-Level Quantitative Mathematics":
Calculus: A Modern Approach - Jeff Knisley & Kevin Shirley
Linear Algebra and Its Applications - David C. Lay
Calculus of Several Variables - Serge Lang
Ordinary Differential Equations – Morris Tenenbaum
Introduction to Partial Differential Equations with Applications - E. C. Zachmanoglou & D. W. Thoe
Note: Standard set of topics that define an early STEM education.