Detailed process of LIM (x → 1) lncos (x-1) / (1-sin (π X / 2))

Detailed process of LIM (x → 1) lncos (x-1) / (1-sin (π X / 2))

lim(x→1) lncos(x-1)/(1-sin(πx/2))
Let X-1 = t, t → 0
The original formula = LIM (t → 0) lncost / (1-sin (π (T + 1) / 2))
=lim(t→0) lncost/(1-cos(πt/2))
=lim(t→0) -sint/cost/(π/2*sin(πt/2))
=-2/πlim(t→0) sint/sin(πt/2)
=-2/π*2/π
=4/π^2