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NIntegrate & Integrate

• To: mathgroup at smc.vnet.net
• Subject: [mg100048] NIntegrate & Integrate
• From: Konstantin <kzhuravl at mtu.edu>
• Date: Fri, 22 May 2009 01:47:50 -0400 (EDT)

Hello everybody,

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? Any help is appreciated. Thanks

Konstantin

• Follow-Ups:
  • Re: NIntegrate & Integrate
    • From: peter <plindsay.0@gmail.com>