lim(x趨向於無窮大時)x^2[1-cos(1/x)]

lim(x趨向於無窮大時)x^2[1-cos(1/x)]

lim x->∞x²;[1 - cos(1/x)]
= lim x->∞[1 - cos(1/x)] /(1/x²;)(分子,分母同時趨向於0,可利用洛必達法則)
= lim x->∞{0 - [-sin(1/x)] * [-x^(-2)]} / [-2x^(-3)]
= lim x->∞[sin(1/x)] /(2/x)(分子,分母同時趨向於0,可利用洛必達法則)
= lim x->∞[cos(1/x)*(1/x)'] /(2/x)'
= lim x->∞[cos(1/x)] / 2
= cos(0)/ 2
= 1/2