Algebra is a branch of mathematics that deals with symbols, variables, and the rules for manipulating them to solve equations and study relationships between mathematical expressions. In algebra, letters (usually represented by symbols like x, y, a, b, etc.) are used to represent unknowns, and various operations like addition, subtraction, multiplication, and division are applied to these symbols following certain rules. Trigonometry is a branch of mathematics that deals with the study of relationships involving the angles and sides of triangles. It is an essential field of mathematics that has applications in various fields, including physics, engineering, astronomy, and architecture.