3. (a) Evaluate dy dx when x = and y = sinx. [2 marks] (b) Estimate the first derivative of y = sinx at x = using a value of for h by each 12 of the following. Forward difference approximation of O(h). Backward difference approximation of O(h). Central difference approximation of O(h2). [6 marks] (c) Estimate the true percentage relative error & for the central difference approximation determined in (b). [2 marks]