1.575。 The root sign is a mathematical symbol. The root sign is a symbol used to represent the root operation of a number or an algebra. If a? =b, then A is the n-th root of B or A is the 1/n power of B. The n-th handwriting and printing are represented by n √, and the number of roots or algebraic expressions are written in the area surrounded by the left √ above the symbol and the lower part of a horizontal part, which cannot be crossed. The radical sign of 3.9 12 is equal to 1.575.