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 Summary ```#include double log10 ( double val); /* value to take common logarithm of */ ``` Description 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 10x = val For example, log10(120) = log10(102 × 1.2) = 2 + log10(1.2) ≈ 2 + 0.079181 or 2.079181 Return Value The log10 function returns the floating-point common logarithm of val. If x < 0, log10 returns NaN. If x = 0, log10 returns -INF. See Also Example ```#include #include /* 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); } ```

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