nynw.net
当前位置:首页 >> tAn3x-sin2x/sin5x的极限怎么算 3x-2x/5x也是1/5... >>

tAn3x-sin2x/sin5x的极限怎么算 3x-2x/5x也是1/5...

这种做法是错的 等价替换适用于乘、除,不适用加减。当你学到泰勒公式之后,你就明白为什么。 (x→0)lim(tan3x-sin2x)/sin5x=(x→0)lim(tan3x-sin2x)/5x =(x→0)lim(3sex3x-2cos2x)/5=(x→0)lim(3-2)/5=1/5

积化和差公式: sinαcosβ=1/2[sin(α+β)+sin(α-β)] 本题中,将3x看做α,2x看做β: sin3xcos2x = 1/2[sin(3x+2x)+sin(3x-2x)] = 1/2(sin5x+sinx)

由cos5x=cos(3x+2x) =cos3xcos2x-sin3xsin2x ① cosx=cos(3x-2x) =cos3xcos2x+sin3xsin2x ② ②-①得 cosx-cos5x=2sin3xsin2x 即sin3xsin2x=1/2(cosx-cos5x) 则sin3xsin2xdx=[1/2(cosx-cos5x)]dx =1/2cosxdx-1/2cos5xdx =1/2sinx-1/2*1/5sin5x =...

lim(sin3x/sin5x) x趋近于0 =lim3/5(5xsin3x/3xsin5x) x趋近于0 =3/5 lim[2x²/(1-cosx)]x趋近于0 =lim[2x²/(2sin^x)]x趋近于0 =1

cos(A-B) = cosAcosB+sinAsinB A=3x, B =2x cos2xcox3x-sin2xsin3x =cos(2x+3x) =cos5x

sin2xcos3x =1/2[sin(2x+3x)+sin(2x-3x)] =1/2(sin5x-sinx)

根据公式sinacosb=1/2(sin(a+b)+sin(a-b))得 sin2xcos3x=1/2(sin(2x+3x)+sin(2x-3x)) =1/2(sin5x+sin(-x)) =(sin5x-sinx)/2

解:先判断条件:都是符合的 0/0型 1 原式=lim[e^x+e^x]/cosx 再判断条件 不符合了,于是原式=2 2.原式=lim3cos3x/5cos5x 再判断条件 不符合了,于是原式=3/5 3.原式=limx/tan2x=lim(1+4x^2)/2 再判断条件 不符合了,于是原式=1/2

x->0 √(1+x)~ 1+(1/2)x √(1+x) -1 ~ (1/2)x lim(x->0) sin2x/[√(1+x)-1] =lim(x->0) 2x/[(1/2)x] =4 ---------------- lim(x->∞) (5x²+2/3x+1)sin/x 题目不清楚 -------------------- x->0 cos√x ~ 1 -(1/2)x lim(x->0+) (cos√x)^(1/x...

1.sin2x=sin(x-π/3) 则2x=2kπ+(x-π/3)或2x=π-(2kπ-π/3)+2kπ 所以x=2kπ-π/3 或x=4π/9+2kπ/3 2.cos(2x-π/6)=sin(3x-π/3) sin(π/2-(2x-π/6))=sin(3x-π/3) sin(2π/3-2x)=sin(3x-π/3) 则2π/3-2x=2kπ+(3x-π/3)或2π/3-2x=π-(3x-π/3)+2kπ 所以化简:x=(...

网站首页 | 网站地图
All rights reserved Powered by www.nynw.net
copyright ©right 2010-2021。
内容来自网络,如有侵犯请联系客服。zhit325@qq.com