Re: NIntegrate & Integrate

*To*: mathgroup at smc.vnet.net*Subject*: [mg100094] Re: NIntegrate & Integrate*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Fri, 22 May 2009 23:42:10 -0400 (EDT)

On 5/22/09 at 1:47 AM, kzhuravl at mtu.edu (Konstantin) wrote: >Easy question for Mathematica. Evaluate definite integral: 2*Cos[x] >from 8.76 to 4.56. >I have evaluated it three different ways: Integrate, NIntegrate and >Integral sign from basic math input palette. >Here is the code(without Integral sign from basic math input >palette): >Clear[x] >{a, b} = {8.76, 4.56}; >NIntegrate[2*Cos[x], {x, a, b}] >Clear[x] >Integrate[2*Cos[x], {x, a, b}] >My output is: >3.21059(NIntegrate) >-3.21059(Integrate) >The right answer is -3.21059. >Why does NIntegrate gave me wrong answer? I cannot reproduce your results above. I get the correct value by simply pasting your code up to the line for NIntegrate into a fresh session. That is: In[1]:= {a, b} = {8.76, 4.56}; NIntegrate[2*Cos[x], {x, a, b}] Out[2]= -3.21059 In[3]:= $Version Out[3]= 7.0 for Mac OS X x86 (64-bit) (February 19, 2009)