(2cosa–8sina+10)/(4sina–cosa+5), если tga=0,25

Cos²a=1:(1+tg²a)=1:(1+1/16)=1:17/16=16/17
cosa=4/√17
sina=√(1-cos²a)=√(1-16/17)=√(1/17)=1/√17
(2cosa-8sina+10):(4sina-cosa+5)=
=(8/√17-8/√17+10):(4/√17-4/√17+5)=10:5=2