In the ICSE Class 9 Mathematics curriculum, the topic of trigonometric ratios of standard angles typically involves understanding the trigonometric functions (sine, cosine, and tangent) of specific angles commonly referred to as standard angles. Here’s a summary:

1. **Definition of Trigonometric Ratios**: Trigonometric ratios are defined based on the sides of a right triangle relative to its acute angle. The main ratios are sine (sin), cosine (cos), and tangent (tan).

2. **Standard Angles**: In trigonometry, certain angles have well-defined trigonometric ratios. These include 0°, 30°, 45°, 60°, and 90°, which correspond to special triangles or common angles encountered in geometry and real-world applications.

3. **Trigonometric Table**: Students learn to construct a trigonometric table or use calculators to find the values of sine, cosine, and tangent for standard angles. These values are often memorized for convenience.

4. **Properties of Trigonometric Ratios**: Students explore the properties of trigonometric ratios, such as the range of values they can take and their relationships with each other. For example, the sine of an angle is always less than or equal to 1.

5. **Application Problems**: Trigonometric ratios of standard angles are applied to solve various problems involving angles and lengths in triangles. This includes finding unknown side lengths or angle measures in right triangles.

6. **Graphical Representation**: Students may also learn about the graphical representation of trigonometric functions on the unit circle or Cartesian plane, which helps visualize the behavior of these functions for different angles.

Overall, mastering the trigonometric ratios of standard angles is essential for understanding more advanced concepts in trigonometry and calculus, as well as for solving problems in geometry, physics, and engineering.