Final answer:
A complex conjugate is the element of a complex number that has the same real part but an opposite-sign imaginary part, and multiplying a complex number by its conjugate yields a real number.
Step-by-step explanation:
A complex conjugate in mathematics is a paired element of a complex number that has the same real part but an opposite-sign imaginary part. When you have a complex number, let's call it A, which can be expressed in the form (a + ib) where 'a' is the real part and 'b' is the imaginary part, the complex conjugate of A, denoted as A*, would be (a - ib). One important property of complex conjugates is that when you multiply a complex number by its conjugate, you get a real number. This is because the product A* A = (a + ib) (a - ib) = a² + b².
For example, if a complex number is a = 3 + 4i, its complex conjugate would be a* = 3 - 4i. Multiplying a by its conjugate, we get a* a = (3 + 4i) (3 - 4i) = 9 + 16 = 25, which is a real number. This property is very useful, especially in fields such as quantum mechanics, where physical measurements must yield real numbers.