x趋向0,x^2 ·(sin1/x)/sin2x的极限

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x趋向0,x^2 ·(sin1/x)/sin2x的极限

x趋向0,x^2 ·(sin1/x)/sin2x的极限
x趋向0,x^2 ·(sin1/x)/sin2x的极限

x趋向0,x^2 ·(sin1/x)/sin2x的极限
x^2 ·(sin1/x)/sin2x
=x/sin(2x)*[x*sin(1/x)] ,
由于 x/sin(2x) 极限为 1/2 ,x*sin(1/x) 极限为 0 (因为 sin(1/x) 有界),
所以所求极限为 0 .

lim(x->0) x^2 ·sin(1/x) /sin(2x)
|sin(1/x)|<=1
lim(x->0) x^2/sin(2x)
=lim(x->0) x^2/(2x) =0
lim(x->0) x^2 ·sin(1/x) /sin(2x) =0

x趋向0, x^2 ·(sin1/x)/sin2x
用价无穷小替换:sin1/x:1/x  sin2x :2x
替换后原式变为:
x^2 ·1/x/2x=x^2 /2x^2=1/2