(a) Along x=π, the limit is:
(x,y)→(π,π/2)limcosysinx=y→π/2limcosy0=0.
(b) Along y=x−π/2, the limit is:
(x,y)→(π,π/2)limcosysinxApply L’Hoˆpital’s Rule:=x→πlimcos(x−π/2)sinx=x→πlim−sin(x−π/2)cosx=1.
Since the limits along the lines x=π and y=x−π differ, the overall limit does not exist.