Whether you are a high school student or a freshman in college or just an ordinary person, if you are interested in learning calculus you need to bury your face in my book. Read it at least 10 to 15 times, back and forth! There are a lot of questions which you are challenged to solve. Have fun with that!
This is the second volume of a series that covers the base-line knowledge you need to go deep into calculus. This volume covers all the topics on the functions, including "Algebraic Functions", "Trigonometric Functions", "Periodic Functions", and many more. Just enjoy reading through the book and make sure to solve all the questions and problems. Don't leave anything behind. Do your best...