In the 10th Grade ICSE Mathematics textbook, the formulas of trigonometry are typically covered in Chapter X: Trigonometry. Some of the important formulas include:

1. **Sine Formula**:
- sin(A) = perpendicular/hypotenuse
- sin(B) = base/hypotenuse
- sin(C) = perpendicular/base

2. **Cosine Formula**:
- cos(A) = base/hypotenuse
- cos(B) = perpendicular/hypotenuse
- cos(C) = base/perpendicular

3. **Tangent Formula**:
- tan(A) = perpendicular/base
- tan(B) = base/perpendicular
- tan(C) = perpendicular/base

These formulas are used to solve problems involving right-angled triangles and trigonometric ratios. Remember to practice using these formulas to become more familiar with them.