First, add a # include "math.h" to the main () function, because the root sign belongs to the function in the mathematical function. To use the root symbol, please add # include "math.h", \ r \ and then add a sqrt before the number to be rooted. \ r \ n For example, \ r \ n # contains. \r\n printf ("Please enter a number:"); \r\n scanf("%f "，& ampa)； \ r \ n b = sqrt(a)； \r\n printf("%f\n "，b)； \r\n \r\n} This program is the result after the user inputs a number and then outputs the root sign of the original value.