Square root any nonnegative number, then the principal square root of −"x" is The right side (as well as its negative) is indeed a square root of −"x", since For every non-zero complex number "z" there exist precisely two numbers "w" such that : the principal square root of "z" (defined below), and its negative. There are two complex numbers that square to a given arbitrary non-zero imaginary number formula_11 with real formula_12 where the two-digit pattern {3, 6} repeats over and over again in the partial denominators. Since , the above is also identical to the following generalized continued fractions: The
Square root of a 2 by 2 matrix pairs: If "R" is a square root of "M", then –"R" is also a square root of "M", since (–"R")(–"R") = (–1)(–1)("RR") = "R" = "M". Let where "A", "B", "C", and "D" may be real or complex numbers. Furthermore, let "τ = A + D" be the trace of "M", and "δ = AD – BC" be its determinant. Let "s" be such that "s" = "δ", and "t" be such that "t" = "τ" + 2"s". That is, Then, if "t" ≠ 0, a square root of "M" is Indeed, the square of "R" is Note that "R"