lim(x→1)lncos(x-1)/(1-sin(pi x/2))상세 과정

lim(x→1)lncos(x-1)/(1-sin(pi x/2))상세 과정

lim(x→1) lncos(x-1)/(1-sin(πx/2))
x-1=t,t→0
원 식=lim(t→0)lncost/(1-sin(pi(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