2021 ASRJC P1 Q6

2021 ASRJC P1 Q6

3 marks
Prelims
  1. Evaluate \(\displaystyle\displaystyle \displaystyle\int_{-a}^{a}{\left| {{x}^{2}}+1-{{\mathrm{e}}^{x}} \right|\,}\mathrm{d}x\) where \(a>0\), giving your answer in terms of \(a\).[3]
  2. By means of substituting \(x=\tan \theta \), or otherwise, show that
    \(\displaystyle\displaystyle \displaystyle\int{\frac{{{x}^{2}}}{{{\left( 1+{{x}^{2}} \right)}^{2}}}\,\mathrm{d}x}=\frac{1}{2}\left( {{\tan }^{-1}}x+\mathrm{f}\left( x \right) \right)+c\),
    where \(c\) is an arbitrary unknown constant and \(\mathrm{f}\left( x \right)\) is an expression to be determined in non-trigonometric form.[4]

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Answer:(a) \(\mathrm e^{-a}+\mathrm e^a-2\) (b) \(f(x)=-\dfrac{x}{1+x^2}\)

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