In 9th grade, mathematics students typically study advanced algebraic concepts, geometric principles, and introductory trigonometry. Here are some common topics:

Algebra

1. Equations and Inequalities: Solving linear and quadratic equations, and graphing linear inequalities.
2. Functions: Understanding domain, range, and composition of functions, including linear, quadratic, and exponential functions.
3. Systems of Equations: Solving systems of linear equations using substitution, elimination, and graphical methods.

Geometry

1. Points, Lines, and Planes: Understanding basic geometric concepts, including points, lines, planes, and angles.
2. Properties of Lines and Planes: Studying properties of parallel, perpendicular, and skew lines, and planes.
3. Angles and Measurement: Understanding types of angles, including acute, obtuse, and right angles, and calculating perimeter and area of various shapes.

Trigonometry

1. Introduction to Trigonometry: Understanding basic trigonometric concepts, including sine, cosine, and tangent.
2. Angles and Triangles: Studying properties of triangles, including right triangles, and calculating trigonometric ratios.

Data Analysis and Graphing

1. Data Analysis: Understanding and interpreting data, including graphs, charts, and tables.
2. Graphing: Graphing linear and quadratic equations, and understanding graphing concepts, including x- and y-intercepts.

Problem-Solving and Modeling

1. Mathematical Modeling: Using mathematical models to solve real-world problems.
2. Problem-Solving Strategies: Developing problem-solving strategies, including drawing diagrams, using algebraic methods, and checking solutions.