A^2 -10a+25=(a-5)^2
при а =135
(135-5)^2=130^2=16900
Sin²t=1:(1+ctg²t)=1:(1+441/400)=1:841/400=400/841
sint=20/29
cost=-√(1-sin²t)=-√(1-400/841)=-√(441/841)=-21/29
tgt=sint/cost=20/29;(-21/29)=-20/29*29/21=-20/21
или tgt=1/ctgt=1:(-21/20)=-20/21
A)cos²t+sin²t=1
б)sint*(-ctgt)=sint*(cost/sint)=-cost
в)-tgt*cost+sint=-sint/cost*cost+sint=-sint+sint=0