The document is about trigonometry and includes:
1. An introduction to trigonometry defining opposite, adjacent, and hypotenuse sides of a right triangle.
2. Exercises labeling the sides of example triangles and defining the trigonometric functions sine, cosine, and tangent.
3. More exercises calculating trigonometric functions based on given side lengths of triangles.
4. Examples solving for unknown side lengths using trigonometric functions.
The document was written by Airil Bin Ahmad and covers basic trigonometry concepts and applications to right triangles.