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Author Comment/Response
jf
09/09/11 09:43am

You can use Chop after the fact,

In[1]:= Integrate[(0.5*(Sin[s/R])^3 - Sin[s/R]*(Cos[s/R])^2)/R^2, {s,
0, s}]

Out[1]= (2.77556*10^-17 - 0.5 Cos[s/R] + 1.66533*10^-16 Cos[s/R]^2 +
0.5 Cos[s/R]^3)/R

In[2]:= Chop[%]

Out[2]= (-0.5 Cos[s/R] + 0.5 Cos[s/R]^3)/R

Or make the 0.5 an exact number,

In[3]:= Integrate[((1/2)*(Sin[s/R])^3 - Sin[s/R]*(Cos[s/R])^2)/R^2, {s, 0, s}]

Out[3]= -((Sin[s/R] Sin[(2 s)/R])/(4 R))

The two results are equivalent.

In[4]:= FullSimplify[ % - %%, Element[{R, s}, Reals]]

Out[4]= ((0. + 0. I) - (2.22045*10^-16 + 0. I) Cos[s/R] - (2.77556*10^-17 + 0. I) Cos[(3 s)/R])/R

In[5]:= Chop[%]

Out[5]= 0

Floating-point approximate numbers are difficult for Integrate and Solve. This is a Mathematics issue, not Mathematica.



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Subject (listing for 'Trigonometric Integration')
Author Date Posted
Trigonometric Integration Malay 09/09/11 02:27am
Re: Trigonometric Integration jf 09/09/11 09:43am
Re: Re: Trigonometric Integration Malay 09/25/11 07:13am
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