realize that 1−cos2x=sin2x due to the trigonometric identity sin2x+cos2x=1
therefore the top equation becomes sin(x)⋅x2⋅sin(x) which is equal to x2⋅sin2(x), after removing the common factors x2 of the denominator and the numerator, you are left with sin2(x)x4
the sin2 function has its domain over only 1 and 0 so it will never be negative or more than that and the bottom function x4 gets smaller and smaller as x approaches 0, so the top function which is a number between 0 and 1 is divided by an increasingly small number, so the limit of the whole function as x approaches 0 is positive Infinity