Derive Equations 2.170 and 2.171. Hint: Use Equations 2.168 and 2.169 to solve for C and D in terms of F:
C=[sin(la)+ilkcos(la)]eikaF;D=[cos(la)−ilksin(la)]eikaF.
Plug these back into Equations 2.166 and 2.167. Obtain the transmission coefficient, and confirm Equation 2.172.