Hi.

These are the important topics for JEE Mains B.Arch under Maths --

1. Trigonometry

2. Coordinate Geometry

3. Algebra topics such as Matrices, Determinants, Quadratic Equations, Binomial Theorem.

4. Heights and Distances, Statistics, Logarithms.

5. 3D Geometry

If you have a further specific query please feel free to comment.

Best of Luck.