Hey guys, I'm trying to use feval to evaluate a very complicated trig function (as in, the fourth derivative of f(x) = log10(tan x)) at a particular point, x = 1.09. I got the fourth derivative no problem, but I'm new at Matlab, and I cannot figure out how to evaluate the function at the given x = 1.09. Can someone show me SPECIFICALLY how to do this? I am lost.