Int gives wrong answer

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Ali M 2022-3-2

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评论： Ali M 2022-3-5

在 MATLAB Online 中打开

syms x

f(x) = cos(x)*sin(x);

Fx = int(f,x)

Fx(x) =

sin(x)^2/2

while the correct answer is -cos(x)^2/2

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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 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 2022-3-2

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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'