1) ctgt*sin^2t=(cost/sint)*sin^2t=cost*sint
2) (tgt+ctgt)^-1=((sint/cost)+cost/sint))^-1=((sin^2t+cos^2t)/(cost*sint))^-1=(1/(cost*sint))^-1=cost*sint
1)=2) cost*sint=cost*sint
1) ctgt*sin^2t=(cost/sint)*sin^2t=cost*sint
2) (tgt+ctgt)^-1=((sint/cost)+cost/sint))^-1=((sin^2t+cos^2t)/(cost*sint))^-1=(1/(cost*sint))^-1=cost*sint
1)=2) cost*sint=cost*sint