Digital root number is the number mod 11 (Ɛ), for example, 1972 is 1 + 9 + 7 + 2 = 19 = 17 which is 1 + 7 = 8, while in decimal the root of the same number (3110) is 5; and in base 16 a digital root of a number is the number mod 15 (0xF), for example, 0x7DF is 7 + 13 + 15 = 35 = 0x23 which is 2 + 3 = 5, while in decimal the root of the same number (2015) is 8. Digital roots form an important mechanic in the visual novel adventure
Square root of a 2 by 2 matrix use the simplified formula where "a" = ±√"A" and "d" = ±√"D"; which, for the various sign choices, gives four, two, or one distinct matrices, if none of, only one of, or both "A" and "D" are zero, respectively. Because it has duplicate eigenvalues, the 2×2 identity matrix formula_10 has infinitely many symmetric rational square roots given by where is any Pythagorean triple—that is, any set of positive integers such that formula_12 In addition, any non-integer, irrational, or complex values of "r, s, t" satisfying formula_13 give square root matrices. The identity matrix also has infinitely many non-symmetric square roots.