lim(x-0)(sin3x*sin5x)/(x^2)

问题描述:

lim(x-0)(sin3x*sin5x)/(x^2)

3X*5X/X^2=15

=15*lim(x-0)(sin3x*sin5x)/(3x*5x)
=15*lim(3x-0)(sin3x)/(3x)*lim(5x-0)(sin5x)/(5x)
=15

当 x → 0 时,
lim (sin3x sin5x) / x²
= 15 lim sin3x/(3x) × sin5x /(5x)
= 15 × 1 × 1
= 15