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2Â¥2012-04-06 16:48:11
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dbb627

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¹þ¹þàÞ: ½ð±Ò+5, ¡ï¡ï¡ï¡ï¡ï×î¼Ñ´ð°¸ 2012-04-06 17:31:30
xiegangmai: ½ð±Ò+2, ллӦÖú£¡ 2012-04-11 22:39:46
0.4937

>> t=int(exp(-(x-1).^2).*log2(1+exp(-4*x)),x,-inf,inf)
Warning: Explicit integral could not be found.  

t =

int(log(1/exp(4*x) + 1)/(exp((x - 1)^2)*log(2)), x = -Inf..Inf)

>> vpa(t)

ans =

0.49371420056718206609671433486689

>> F=@(x)exp(-(x-1).^2).*log2(1+exp(-4*x));
Q1=quadgk(F,0,inf)
Q2=quadgk(F,-inf,0)
Q3=quadgk(F,-150,0)

Q1 =

    0.1705

Warning: Infinite or Not-a-Number value encountered.
> In quadgk>vadapt at 290
  In quadgk at 216

Q2 =

   NaN


Q3 =

    0.3232

>> Q1+Q3

ans =

    0.4937

>>
The more you learn, the more you know, the more you know, and the more you forget. The more you forget, the less you know. So why bother to learn.
3Â¥2012-04-06 17:14:31
ÒÑÔÄ   »Ø¸´´ËÂ¥   ¹Ø×¢TA ¸øTA·¢ÏûÏ¢ ËÍTAºì»¨ TAµÄ»ØÌû

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гæ (³õÈëÎÄ̳)

ÒýÓûØÌû:
3Â¥: Originally posted by dbb627 at 2012-04-06 17:14:31:
0.4937

>> t=int(exp(-(x-1).^2).*log2(1+exp(-4*x)),x,-inf,inf)
Warning: Explicit integral could not be found.  

t =

int(log(1/exp(4*x) + 1)/(exp((x - 1)^2)*log(2)), x = -Inf..Inf)
...

ÏëÎÊһϣ¬vpaÄÜÔÚmÎļþÀïÓÃÂ𣿿ÉÒԵϰÔõôÓã¿
vpa(t)»¹ÊÇt=vpa(t),²»¹ýºÃÏñ¶¼ÔËÐв»³öÀ´
4Â¥2012-04-11 16:58:31
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