Hi all, The following is part of a part, of an assignment for my matlab course for uni. For most of the ODE solvers in matlab you also have to be able to solve the question numerically - and this is the component of the question i'm doing here.. The equilibrium equation of an arch type structure is the function below.. P = 4 x K x L[cos(alpha -theta ) - cos(alpha)] x tan(alpha -theta ); GIVEN L=1m, alpha=30degrees, K=100kN/m Substituting in unknowns we get.. P = 400[cos(30 - theta) - cos(30)] x tan(30 - theta) Now I have a function of P(force) and theta(angle in degs), for the question though I have to solve for the roots using 'Newtons Method'(need the derivative of the function) and this is where my questions comes in.. To find the derivative of this function with respect to theta, do I first need to convert theta to radians? ie, alpha = Pi / 6, Theta = Pi / 180(theta) ?? ..should I be taking the derivative of the above function? or the one below P = 400[cos(Pi/6 - Pi/180(theta)) - cos(Pi/6)] x tan(Pi/6 - Pi/180(theta)) Thanks for reading!