问题标题:
求极限:lim(n→∞)2^nsinx/2^n(x不为零的常数);lim(x→0)(tanx-sinx)/x^3;lim(x→a)(sinx-sina)/(x-alim(x→π/3)sin(x-π/3)/(1-2cosx)希望写写过程,
问题描述:
求极限:lim(n→∞)2^nsinx/2^n(x不为零的常数);lim(x→0)(tanx-sinx)/x^3;lim(x→a)(sinx-sina)/(x-a
lim(x→π/3)sin(x-π/3)/(1-2cosx)希望写写过程,
傅军回答:
①等价无穷小量替换:
lim(n→∞)2^nsin(x/2^n)
=lim(n→∞)2^n*(x/2^n)
=x
②
【罗必塔法则】
lim(x→0)(tanx-sinx)/x^3
=lim(x→0)(sec^2x-cosx)/3x^2
=lim(x→0)(2sec^2xtanx+sinx)/6x
=lim(x→0)(2sec^2x/cosx+1)*sinx/6x
=3*(1/6)
=1/2
③
lim(x->a)[sinx-sina]/[x-a]
=lim(x->a){2cos[(x+a)/2][sin(x-a)/2]}/[x-a]
=lim(x->a)cos[(x+a)/2]*{2[(x-a)/2}/[x-a]
=cosa
④
【罗必塔法则】
lim(x→π/3)sin(x-π/3)/(1-2cosx)
=lim(x→π/3)cos(x-π/3)/2sinx
=1/(2*1/2)
=1
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