The following summation/subtraction rule is especially useful in probability theory when one is dealing with a sum of log-probabilities:

which gives the special cases:

Note that in practice formula_32 and formula_5 have to be switched on the right hand side of the equations if formula_34. Also note that the subtraction identity is not defined if formula_35 since the logarithm of zero is not defined.

More generally:

where formula_37.

परिभाषाएँ
घातों का कैंसिल होना (Canceling exponentials)
संकलन/ब्यकलन (Summation/subtraction)
स्वयंस्पष्ट सर्वसमिकाएँ (Trivial identities)