[tex]\lim_{x \to \ y} \frac{cos 2x - cos 2y}{ x^{2} }[/tex]

lim x --> y
= (cos 2x - cos 2y)/(x²)
= (-2 sin 2x + 2 sin 2y)/(2x)
= -2(sin 2x - sin 2y)/(2x) ---------->> (masukkan nilai "x --> y")
= -2(sin 2y - sin 2y)/(2y)
= -2(2 cos 2y)/(2y)
= -2(2)/1
= -4