**Question:**What is Power Function in Standard C Library?

**Answer:** There are two functions in this family which are defined in ‘math.h’ header and are prototyped below

double pow(double x, double y); double sqrt(double value);

Power ‘pow()’ function returns x raised to power y. Since logarithms may be used to compute the exp. ‘x^y’, x can’t be negative and y can’t be non-integer. If, this is so, domain error occurs!

/* fp_pow_fun.c -- pow() function computes exp. of forms 'x^y' */ #include <stdio.h> #include <stdlib.h> #include <math.h> int main(void) { double x, y, result; printf("User, enter +ve value for 'x' and Integral Value for 'y' " "to evaluate \"x^y\"...\n"); printf("Power \"x^y\" with -ve 'x' and Non-Integral 'y' " "causes DOMAIN ERROR!\n"); scanf("%lf %lf", &x, &y); /* pow() function executes */ result = pow(x, y); /* Display the result */ printf("Pow \"%lf^%lf\" : %lf\n", x, y, result); return 0; }

Example of Square-Root ‘sqrt()’ function:

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/* fp_sqrt_fun.c -- sqrt() function computes square-root of +ve values */ #include <stdio.h> #include <stdlib.h> #include <math.h> int main(void) { double sqrt_of, result; printf("User, enter +ve value of which you seek Square-Root of...\n"); printf("Square-Root of Negative Values causes DOMAIN ERROR!\n"); scanf("%lf", &sqrt_of); /* sqrt() function executes */ result = sqrt(sqrt_of); /* Display the result */ printf("Square-Root of \"%lf\": %lf\n", sqrt_of, result); return 0; }

Output for some arbitrary values as follows:

User, enter +ve value of which you seek Square-Root of... Square-Root of Negative Values causes DOMAIN ERROR! 5 Square-Root of "5.000000": 2.236068 User, enter +ve value of which you seek Square-Root of... Square-Root of Negative Values causes DOMAIN ERROR! -10 Square-Root of "-10.000000": -nan

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