In mathematics, addition and subtraction logarithms or Gaussian logarithms can be utilized to find the logarithms of the sum and difference of a pair of values whose logarithms are known, without knowing the values themselves. Their mathematical foundations trace back to and Carl Friedrich Gauss in the early 1800s. The operations of addition and subtraction can be calculated by the formula: where , , the "sum" function is defined by , and the "difference" function by . The functions and are also known as Gaussian logarithms.