Int gives wrong answer

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Ali M
Ali M 2022-3-2
评论： Ali M 2022-3-5
Ran in:
syms x
f(x) = cos(x)*sin(x);
Fx = int(f,x)
Fx(x) = 
Fx(x) =
sin(x)^2/2
while the correct answer is -cos(x)^2/2
  3 个评论
显示 1更早的评论
Torsten
Torsten 2022-3-2
Since sin(x)^2/2 = -cos(x)^2/2 + 1/2, both answers are correct.
Note that both answers only differ by a constant, namely 1/2.
Ali M
Ali M 2022-3-5
Thanks @Torsten & @Robin Merkle! @Torsten I would vote for you but I cant, your is a comment not an answer

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回答（1 个）

Walter Roberson
Walter Roberson 2022-3-2
Remember that indefinite integration always has an implied "plus a constant". So any two results of int() that differ by a constant are the same integral result. And sin squared plus cos squared equals 1 so the two possibilities are the same up to the constant.
You can ask to rewrite() to 'cos'

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