∵ α∈（π，3π/2）∴ sinα<0又∵cosα=-5/13∴sinα=-12/13∴tanα=12/5sin2α=2sinαcosα=120/169cos2α=1-2（sinα）^2=-119/169tan2α=2*tanα/[1-(tanα)^2]=-120/119
