（1+tanα+cotα)/(1+tan^2α+tanα)-cotα/(1+tan^2α)=cotα(tanα+tan^2α+1)/(1+tan^2α+tanα)-cotα/(1+tan^2α)=cotα(1-1/(1+tan^2α))=cotα*tan^2α/(1+tan^2α)=tanα/(1+tan^2a)=sinα/cosα*(1+sin^2α...