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    10i

    I have subbed in sin x

    And got 1/cos^3x ... What next?
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    (Original post by IShouldBeRevising_)


    10i

    I have subbed in sin x

    And got 1/cos^3x ... What next?
    Post your working. This is a lot simpler.
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    Firstly x = \sin{\theta} and then find dx in terms of d\theta. Finally, find the limits in terms of \theta and evaluate the integral.
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    Right now your integral is

     \int \frac{1}{cos^3(\theta)} dx

    You can't integrate  \theta with respect to 'x'. What have you still got to do?
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    Put dx in terms of d\theta, i.e. x = sin(theta) => dx/d(theta) = ...
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    (Original post by IShouldBeRevising_)


    10i

    I have subbed in sin x

    And got 1/cos^3x ... What next?
    If you've put x = sin \theta then you shouldn't have any x terms left in the integral. Your denominator becomes cos^3 \theta, and you need to convert dx to d\theta
 
 
 
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