Lim(x趋于0)(tanx-sinx)/x=
Lim(x\u8d8b\u4e8e0)\uff08x-sinx\uff09/(tanx-x)\u7528\u7b49\u4ef7\u65e0\u7a77\u5c0f\u4ee3\u6362
x\u8d8b\u5411\u4e8e0\u65f6
x-sin(x)\u4e0e(1/6)x\u7684\u7acb\u65b9\u7b49\u4ef7
tan(x)-x\u4e0e(1/3)x\u7684\u7acb\u65b9\u7b49\u4ef7
\u4ee3\u6362,\u7ed3\u679c\u4e3a1/2
\u6ce8\u610fx\u8d8b\u4e8e0\u7684\u65f6\u5019\uff0c
tanx -sinx=tanx *(1-cosx)
\u90a3\u4e48tanx\u7b49\u4ef7\u4e8ex\uff0c
\u800c1-cosx\u7b49\u4ef7\u4e8e0.5x^2\uff0c
\u4e8e\u662f\u5c31\u5f97\u5230
\u539f\u6781\u9650=lim(x->0) x*0.5x^2 /x^3= 0.5
\u6545\u6781\u9650\u503c\u4e3a0.5
详细公式我编辑了一个word文档放在附件里。
x趋于0我就不写了。
lim(tanx-sinx)/x
=lim(sinx/cosx-sinx)/x
=limsinx(1-cosx)/xcosx
=lim(1-cosx)*limsinx/x*lim1/cosx(都有极限,所以可以拆开)
=0*1*1
=0
sinx在x=0处的导数为1,也就是说在0左右的一个极小区间内y=sinx与直线y=x几乎相同,当x趋于0时sinx=x
绛旓細姝g‘瑙f硶锛岀敤娉板嫆鍏紡锛宼anx=x+x^3/3+o(x^3) sinx=x-x^3/3!+o(x^3) e^(x^3)-1=x^3 lim[x-->0](tanx-sinx)/[e^(x^3)-1]=lim[x-->0][x+x^3/3+o(x^3) -x+x^3/3!-o(x^3)]/x^3 =lim[x-->0][x^3/2+o(x^3) ]/x^3 =1/2 浣犵殑绗竴姝ュ氨...
绛旓細鍏蜂綋鍥炵瓟濡備笅锛歺鈫0鏃讹紝e^x鈫1锛宔^(tanx-x)-1绛変环浜巘anx-x 鎵浠^tan-e^x绛変环浜巘anx-x x鈫0鏃讹紝tanx-x绛変环浜巟^n锛=lim(x鈫0) (tanx-x)/x^n =lim(x鈫0) ((secx)^2-1)/nx^(n-1)=lim(x鈫0) (tanx)^2/nx^(n-1)=lim(x鈫0) x^2/nx^(n-1)=lim(x鈫0) x^(3...
绛旓細lim(tanx-sinx)/sin³x =lim(sinx/cosx -sinx)/sin³x =lim(1/cosx -1)/sin²x =lim(1-cosx)/[cosx路(1-cos²x)]=lim(1-cosx)/[cosx路(1+cosx)(1-cosx)]=lim1/[cosx(1+cosx)]=1/[1脳(1+1)]=1/2 鏈闈炲父绠鍗曪紝杩炵瓑浠锋棤绌峰皬閮芥病鏈夌敤鍒帮紝閫氳繃...
绛旓細濡傚浘
绛旓細灏tanx娉板嫆灞曞紑锛屽緱tanx-x涓巟³鍚岄樁锛屽仛姣旂敤娲涘繀杈剧煡tanx-x涓巟³/3涓虹瓑浠烽樁 褰x瓒嬩簬0鏃讹紝鍘熷紡鍖栦负x³/3x²sinx 鍖栫畝寰梮/3sinx 鏋侀檺涓1/3
绛旓細鎵浠^tan-e^x绛変环浜巘anx-x x鈫0鏃讹紝tanx-x绛変环浜巟^n锛=lim(x鈫0) (tanx-x)/x^n =lim(x鈫0) ((secx)^2-1)/nx^(n-1)=lim(x鈫0) (tanx)^2/nx^(n-1)=lim(x鈫0) x^2/nx^(n-1)=lim(x鈫0) x^(3-n)/n n=3 褰撳垎姣嶇瓑浜庨浂鏃讹紝灏变笉鑳藉皢瓒嬪悜鍊肩洿鎺ヤ唬鍏ュ垎姣嶏紝鍙互...
绛旓細^^e^tan-e^x=e^x(e^(tanx-x)-1)锛寈鈫0鏃讹紝e^x鈫1锛宔^(tanx-x)-1绛変环浜巘anx-x銆傛墍浠^tan-e^x绛変环浜巘anx-x銆傛墍浠ワ紝x鈫0鏃讹紝tanx-x绛変环浜巟^n锛屾墍浠 1=lim(x鈫0) (tanx-x)/x^n =lim(x鈫0) ((secx)^2-1)/nx^(n-1)=lim(x鈫0) (tanx)^2/nx^(n-1)=lim(x...
绛旓細1-cos2x=2sin^2 x 鍒欏師寮忓寲绠涓:[(1/cosx)-1]/2sinx =(1-cosx)/(2sinxcosx)=(1-cosx)/(sin2x)娲涘繀杈炬硶鍒欎笂涓嬫眰瀵硷細sinx/2cos2x 鍒欐瀬闄愪负0 楠岀畻浜嗗緢澶氭浜...搴旇鏄瓟妗堥敊浜嗗惂锛
绛旓細tanx 鐨勬嘲鍕掑睍寮寮忔槸 x + 1/3*x^3 + 2/15*x^5 + ...锛屾墍浠 tanx - x ~ 1/3*x^3 銆
绛旓細=1/3 鍗lim锛坱anx-x锛= 锛1/3锛墄^3 寰楄瘉 姝f帹鐢ㄦ嘲鍕掑叕寮忥細f(x)=tanx,f'(x)=(secx)^2,f''(x)=2(secx)^2tanx,f(3)(x)=4(secx)^2(tanx)^2+2(secx)^4 閭d箞f(0)=0,f'(0)=1,f''(0)=0,f(3)(0)=2 tanx=0+x+0+(2/3!)x^3+o(x^3)=x+(1/3)x^3+o(...