Log of −1 (Base 10)

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What is log(−1)?

Answer

log(−1)
does not exist

log here is the common log, base 10.

10 raised to any power is a positive number, so the negative number −1 cannot be reached.

We look for y with 10y = −1.

Oxy

The curve y = log x passes through (1, 0) and (10, 1) and rises: for x > 1 the log is positive, for 0 < x < 1 negative.

The graph exists only to the right of the y-axis: there is no point at x = −1.

Log of −1 in different bases
BaseNotationValue
eln(−1)does not exist
10log(−1)does not exist
2log₂(−1)does not exist

See Also

FAQ

What is log(−1)?

log(−1) does not exist

Does log(−1) exist in complex numbers?

Yes, in complex numbers: the principal value for x < 0 is log x = (ln|x| + iπ) / ln 10, so log(−1) = iπ / ln 10 ≈ 1.3644i. Among real numbers it does not exist.

What is e?

e ≈ 2.71828 is the base of the natural logarithm: ln x is the logarithm of x to base e, so ln e = 1. It is an irrational number, like π.