Problem Integrating sin(2*x)

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Ricardo
Ricardo 2014-3-5
评论： Gustavo Leal 2017-10-9
>> syms x >> f=sin(2*x)
f =
sin(2*x)
>> int(f)
ans =
sin(x)^2
>>
I am sure it is wrong because it should be -1/2+sin(x)^2

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Paul
Paul 2014-3-5
The integral is:
sin(x)^2 + C
but Matlab just doesn't show the constant. How do you get the -1/2? Because if you differentiate the integral (sin(x)^2 + C) you get:
2*sin(x)*cos(x) = sin(2*x)
And the constant differentiated gives 0 since it doesnt depend on x.
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Ricardo
Ricardo 2014-3-5
编辑：Ricardo 2014-3-5
All right, Thanks!!
Gustavo Leal
Gustavo Leal 2017-10-9
sin(pi)^2 != -cos (2pi)/2 ,for example, something its wrong with this function at MATLab

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