Complex
In mathematics, a complex most commonly refers to a complex number, which is a number of the form a + bi, where a and b are real numbers and i is the imaginary unit satisfying i^2 = -1.[1] This extends the real numbers to solve equations like x^2 + 1 = 0, forming the set \mathbb{C}. Complex numbers are visualized as points in the complex plane, with the real part on the horizontal axis and imaginary part on the vertical.[2] The term "complex" has broader applications across fields. In chemistry, it denotes coordination compounds consisting of a central metal atom bonded to ligands. In biology, protein complexes are assemblies of multiple polypeptides performing cellular functions. In psychology, a complex is a cluster of unconscious ideas and emotions influencing behavior. Other uses include geological formations, architectural structures, and concepts in arts and systems theory. See the following sections for detailed explanations.Mathematics
Complex numbers
A complex number is an element of the number system extending the real numbers by including the imaginary unit i, defined by the property i^2 = -1. It is typically expressed in rectangular form as z = a + bi, where a and b are real numbers, with a called the real part \operatorname{Re}(z) and b the imaginary part \operatorname{Im}(z).[3] This construction allows solutions to polynomial equations with real coefficients that have no real roots, such as x^2 + 1 = 0, whose solutions are x = \pm i.[4] Arithmetic operations on complex numbers are defined componentwise for addition and subtraction, and extend the real number operations for multiplication and division. Specifically, for complex numbers z_1 = a + bi and z_2 = c + di:- Addition: z_1 + z_2 = (a + c) + (b + d)i
- Subtraction: z_1 - z_2 = (a - c) + (b - d)i
- Multiplication: z_1 z_2 = (ac - bd) + (ad + bc)i