Calculus I - Derivatives of Trig Functions
tutorial.math.lamar.edu › Solutions › CalcIFeb 06, 2018 · Start Solution. We know that the derivative of the function will give us the slope of the tangent line so we’ll need the derivative of the function. f ′ ( x) = sec 2 ( x) − 9 sin ( x) f ′ ( x) = sec 2 ( x) − 9 sin ( x) Show Step 2. Now all we need to do is evaluate the function and the derivative at the point in question.