Uncertainty propagation
In order to calculate the error of a quantity derived from a mathematical formula which has measured variables with errors, one should use the uncertainty propagation analysis. If the values of these measured components are uncorrelated then their variances (σ^{2}) have to be taken into account. For correlated variables, their covariances have to be considered too. Here we have the variables (A, B) with uncertainties (σ_{A}, σ_{B}) and precisely defined constants (a, b).