4(a+1)/(a³-8)+a/(a²+2a+4)+1/(2-a)=(4a+1+a²-2a)/((a-2)(a²+2a+4))-1/(a-2)=
=(a²+2a+1)/((a-2)(a²+2a+1))-1/(a-1)=(a²+2a+1-a²-2a-1)/((a-2)(a²+2a+1))=
=0/(a³-1)=0.
COSa = 5/13 3п/2 <a<2п
sina=sqrt(1-25/169)=sqrt(144/169)=-12/13
tga=(-12/13)/5/13=-12/5
ctga=5/13/(-12/13)=-5/12
(sina трицателный, т.к угол принадлежит четвёртой четверти ===> 3п/2 <a<2п )
(5+a)/2a² +(1-2a)/a=(5+a+2a(1-2a))/2a²=(5+a+2a-4a²)/2a² =(5+3a-4a²)/2a²