Chang [1] proposed a method to determine the performance of a south facing single-axis tracked panel according to global radiation predicted by empirical model where the mathematic expressions appropriate for single-axis tracking system were derived, partially in [1] and in detail in [2]. The presented, in [2], solar azimuth angle, rotation angle and incidence angle values are not correct. This incorrectness could have its influence on other calculated values. The present comments discuss this incorrectness, correct the above mentioned errors and discuss the sensitivity of other calculated values on the observed errors.