where D is a new constant. (This equation is valid only when the cos2 θ extrapolation function is valid. If some other extrapolation function is used, Eq. (3.8) must be modified accordingly.) The meaning of Eq. (3.9) is that the observed sin2 θ value for any given peak will be in error by the amount D sin2 2θ as a result of the combined action of the systematic errors.