What are some good math books 1st grade highschool student can understand?

Question

I know basic geometry and algebra, I know trigonometry but I don't understand it, I'm willing to learn math but 95% of books are not suited for my knowledge (they are too advanced). What are some good books I can read? I especially like reading proofs and problems whit sigma (series ). Sorry for my bad spelling.

I need advice for learning math:

• Where to start?

• How?

Your story would help too.

P.S. I like some educational channels.

Answer 1

For problem solving first course you can read
Solving Mathematical Problems A Personal Perspective-Terence Tao

For learning counting ways you can read Niven's classic book
Mathematics of Choice How to Count Without Counting-Ivan Niven

For reading elementary calculus you can read
A Course of Pure Mathematics-G. H. Hardy

For number theory I highly recommand you the book
An Introduction to the Theory of Numbers-G. H. Hardy,E. M. Right

Another good book in number theory is
Topics in the Theory of Numbers-Paul Erdos,Janos Suranyi

Answer 2

• The Enjoyment of Mathematics, by Hans Rademacher and Otto Toeplitz;

• What Is Mathematics?, by Richard Courant and Herbert Robbins;

• All books written by George Pólya;

• All books written by Ivan Niven. (P.S. his introductory calculus textbook is very instructive and pleasant to read)