→ suhorng :since cosine is continuous on (-\infty, \infty) 09/18 22:32
→ suhorng :lim_(x->0) cos(x) = cos(lim_(x->0) x) = cos(0)=1 09/18 22:32
推 sato186 :請問一下 要怎麼證明連續性啊? 09/18 23:13
推 jacky7987 :|cos(x)-cos(0)|=|-2sin(x/2)*sin(x/2)| 09/18 23:19
→ jacky7987 :<=2*|x/2|^2<|x|^2/2 let delta=(sqrt(2)epsilon)^2 09/18 23:20