log10

The log10 function calculates the common logarithm for the floating-point number val. The logarithm is the exponent to which the base (10 in the case of common logs) must be raised to equal val. Or,

log₁₀ 10^x = val

For example,

log10(120)
= log10(10² × 1.2)
= 2 + log10(1.2)
≈ 2 + 0.079181 or 2.079181

The log10 function returns the floating-point common logarithm of val.

• If x < 0, log10 returns NaN.
• If x = 0, log10 returns -INF.

exp, log, pow

#include <math.h>
#include <stdio.h> /* for printf */

void tst_log10 (void) {
  float x;
  float y;

  x = 2.718282;
  x *= x;

  y = log10 (x); /* y = 2 */

  printf ("LOG10(%f) = %f\n", x, y);
}