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Size:  296.0 KB for these two questions, I don't get why the u value is set as shown . For part c why is u not cosx ?
    For part e why is u cosx not sinx ??

    Thx
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    (Original post by coconut64)
    for these two questions, I don't get why the u value is set as shown . For part c why is u not cosx ?
    For part e why is u cosx not sinx ??

    Thx
    Because not in all cases would you be picking a substitution based on what is there. These substitutions are based off how their derivatives would help simplify what is inside the integral into something we are more comfortable integrating.
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    You could probably use sin but the given substitution is normally there to make life easier.
 
 
 
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