Trigonometry is a branch of mathematics that deals with the study of relationships involving angles, triangles, and trigonometric functions such as sine, cosine, and tangent. It has a wide range of applications in fields such as physics, engineering, and astronomy.

Some common topics in trigonometry include:

• Trigonometric functions: sine, cosine, tangent, cosecant, secant, and cotangent.
• Right triangles: the relationships between the sides and angles of a right triangle, including the Pythagorean theorem.
• Trigonometric identities: equations that relate trigonometric functions to one another.
• Unit circle: a circle with radius 1 used to define the values of trigonometric functions for any angle.
• Trigonometric equations: equations that involve trigonometric functions and may be solved using various techniques.