Andrew and Tal need your help to compute the average f in the interval [- , ;] 1, " of the function cos 3x sin 4x f (2) = 6 tan' rsec2x 0 B, you find that A = 7 & G and B = 1 B G. (b) Tal suggests that one should also be able to compute J= tan xsec rda. Tal also recalls that, after a certain change of variables, the integral J becomes J = 13 du. The change of variables is u = tan(x) (c) Your tutor appears to you in a vivid dream and gives you the result of some computations that you summarise in the table below. Not all of them will be helpful. cos 3x sin 4x da = 4 3 14 V3 tan' x sec x de = 1 7 36 6 cos 3x sin 4x da = 0 tan' x sec x dr = 0 cos 3x sin 4x da = 4 3 714 V3 tan x sec x de = 1 36 Using the information in your dream, compute the average f in the interval [-, "] of f. f =