lim (x–0) 1–cos10x/1–cos4x
1–cos α =2sin2( α /2) [m]=lim_{x → 0}\frac{2sin^25x}{2sin^22x}=lim_{x → 0}(\frac{sin5x}{sin2x})^2=(\frac{5}{2})^2=\frac{25}{4}[/m]