1-cost=2sin^2(t/2)
(1-cost)/sint=2sin^2(t/2)/2sint/2*cos(t/2)=sin(t/2)/cos(t/2)=tg(t/2)
sin^2t/cost-cos^2t/sint=(sin^3t-cos^3t)/sint*cost
sin^3t-cos^3t=(sint-cost)(sin^t+cos^t+sintcost)=0,5(1+sintcost)
sin^2t/cost-cos^2t/sint=(1/2)(1+sintcost)/(sintcost)
(sint-cost)^=1/4 1-2sintcost=1/4
sintcost=3/8
sin^2t/cost-cos^2t/sint=(1/2)*(1+8/3)=11/6