Example Video Example () If u = xby + y z, where x = rset, y = rs2e-t, and z = 2s sin(t), find the value of - when r = 2, s = 1, t = 0. as Solution With the help of the tree diagram in the figure below, we have au du ax du dy du az as ax as ay as az as x (ret ) + (x6 + 2yz?) (2rse-t) + (7y226) 12 sin ( t) r Ci When r = 2, s = 1, and t = 0, we have x = 2, y = 2, and z = 0, so du = (2 ) + ( 64 ) ( 4 ) + (0 ) ( 0 ) = as