dz se the functions below to (a) express Ju and as functions of u and v both by using the Chain Rule and by expressing z directly in terms of u and v before differentiating. Then (b) evaluate av and 23 z=2 tan x=u cos v, y=usin v. (u,v) = 0.8, dz (a) Express and as functions of x and y. Find dx 20 (Type an exact answer.) at the given point (