Solving Integrals using Substitution | Cosine Functions | Integral Help Needed

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I have been asked to state which one of the following 3 integrals I can solve using integration by substitution

(i) integral cos (x^2) dx

(ii) integral x cos x (x^2) dx

(iii) integral x^2 cos (x^2) dx

I would say that it is (ii) because x is the derivative of x^2 is that the correct answer or is there anything else I should add? Thanks in advance
 
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That would be okay enough, I guess.
 
Well, x isn't the derivative of x^2, but I know what you meant. Maybe you could also show how basic substitution fails on the other two.
 

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