The conversation between human and AI assistant.
What are the toughest mathematics books for the XIth-XIIth standard?
That's great. How about books for geometry?
For geometry, you can try 'Plane Trigonometry and Coordinate Geometry' by S.L. Loney or 'Geometry Revisited' by H.S.M Coxeter and Samuel L. Greitzer. Both books delve deep into the concepts of geometry and pose challenging problems.