作者查詢 / suhorng
作者 suhorng 在 PTT [ trans_math ] 看板的留言(推文), 共282則
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1F推:第二題把cos(t)的泰勒展開中t用x^2帶入61.217.32.242 06/16 21:38
2F→:3.令t=1/x, dx/x^2 = -dt61.217.32.242 06/16 21:39
4F→:yes~61.217.32.242 06/16 22:40
6F→:沒有算...XD61.217.32.242 06/16 22:42
1F推:1-cos(x) = 2sin^2(x/2), let u=x/261.217.32.242 06/14 20:47
2F→:所謂簡化應該是說變成這樣後可以代公式吧?61.217.32.242 06/14 20:47
4F→:第一行代進去 那樣變數變換 則1024=64*8*261.217.32.242 06/14 21:27
5F→:算一下阿61.217.32.242 06/14 21:27
7F推:令 u=x/2, 則 dx = 2 du <-- 這裡來的61.217.32.242 06/14 22:19
8F→:No, f是被積函數, 積分範圍選單位球59.115.148.117 06/09 09:08
3F→:y是變數x是常數61.217.35.109 06/07 08:23
9F→:是吧61.217.35.109 06/07 09:05
1F→:...嗯? xe^(x^2/x) = xe^x 是這樣嗎...61.217.35.109 06/07 00:16
1F推:1.內=6(sec^2(2x)-1)*tan sec,令t=sec(2x)61.217.35.142 06/05 17:18
2F→:第二題的積分範圍會畫嗎? z積完用極座標.61.217.35.142 06/05 17:19
3F→:(直接用原柱座標是一樣意思)61.217.35.142 06/05 17:20
5F→:令 t = sec(2x) 代換61.217.35.142 06/05 17:42
7F→:我代換完是變成∫3(t^2-1)dt @@61.217.35.142 06/05 17:43
9F→:(sec 2x)' = sec 2x tan 2x61.217.35.142 06/05 17:45
10F→: * 261.217.35.142 06/05 17:48
13F→:3(sec^2(2x) - 1)(sec 2x)' = 6tan^3 sec61.217.35.142 06/05 17:56
14F→:(sec 2x)' = sec 2x tan 2x * 261.217.35.142 06/05 17:56
15F→:對61.217.35.142 06/05 17:56
19F推:4 因為6會變361.217.35.109 06/06 08:19
1F→:yes61.217.35.142 06/05 17:33
3F→:Yes, you are right. Now note that61.217.35.142 06/05 15:53
4F→:lim_{u→0} sin(t)/t = 161.217.35.142 06/05 15:53
5F→:So for N large enough, we may replace61.217.35.142 06/05 15:53
6F→:∫[N,x]sin(1/(1+t))dt by∫[N,x]dt/(1+t)61.217.35.142 06/05 15:54
7F→:which diverges to ∞ as x→∞.61.217.35.142 06/05 15:54
8F推:For 3, cos(t)/t^2≧cos(1/2)/t^2, t<1/261.217.35.142 06/05 15:58
9F→:∫(0,1/2] dt/t^2 →∞61.217.35.142 06/05 15:59
10F→:∞-∞可以想辦法弄成0/0或∞/∞ 通分之類61.217.35.142 06/05 16:21
11F→:抱歉 第四行應是lim sin(u)/u = 161.217.35.142 06/05 16:22
15F→:請驗證∫[0,x]sin(1/(1+t))dt以及∫[x,1]61.217.35.142 06/05 20:55
16F→:cos(t)/t^2 dt 都發散 所以第一題是∞/∞61.217.35.142 06/05 20:55
17F→:第三題是0.∞ 都可以試試看l'Hopital61.217.35.142 06/05 20:55
1F推:Gx=0:x(3x-2)+3y(3x-2)=0→(x+3y)(3x-2)=061.217.34.17 06/02 23:57
2F→:1.x=2/3代到Gy=0求y 2.x=-3y代到Gy=0求x,y61.217.34.17 06/02 23:58
1F→:cos(x) + cos(x+y) = 2cos(x+y/2)cos(y/2)61.217.34.17 06/02 21:48
2F→:cos(y) + cos(x+y) = 2cos(x/2+y)cos(x/2)61.217.34.17 06/02 21:48