Hi guys, I did a few sets of test in determining the natural frequency of a crane lifting loads. From that, I tried to find two constant from its initial function. a is the stiffness of the pole that was holding the crane b is the weight of the crane x is the weight of the load The tests were completed by using three different loads on three different position. I plotted the graph as below. From the obtained graph and the initial function, I tried to determine the value of constant A and B. By calculating manually, the value of A and B are not constant but it supposed to be constant. I tried using MATHCAD to find the value of the constants by using nonlinear regression method but I am not convince that is a right solution. Any of you know any mathematical approximation method that I can use?