The phrase “complex number” came in the literature in 1831 with the work of C. F. Gauss.1 This initiation led to many important developments in mathematics. The equations x2 +1 = 0 and x2 +2x+3 = 0 with real coefficients, for example, cannot be satisfied by any real number. Such quadratic equations without real solutions were observed by G. Cardano2 in the middle of the sixteenth century, which led to the introduction of complex numbers.