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Q.Using integration, prove that: ∫ 1/(a² − x²) dx = 1/(2a) log|(a+x)/(a−x)| + c.

Goa GbshseGBSHSE Class 12 Board Exam 2026Subjective· 3mImportance★★★★★
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Factor a2−x2=(a−x)(a+x)a^2-x^2=(a-x)(a+x), split into partial fractions, then integrate term by term.

1a2−x2=1(a−x)(a+x)\dfrac{1}{a^2-x^2} = \dfrac{1}{(a-x)(a+x)}

Write 1(a−x)(a+x)=Aa−x+Ba+x\dfrac{1}{(a-x)(a+x)} = \dfrac{A}{a-x}+\dfrac{B}{a+x}.

Then 1=A(a+x)+B(a−x)1 = A(a+x)+B(a-x). Putting x=ax=a: 1=2aA⇒A=12a1=2aA \Rightarrow A=\dfrac{1}{2a}. Putting x=−ax=-a: 1=2aB⇒B=12a1=2aB \Rightarrow B=\dfrac{1}{2a}.

So 1a2−x2=12a[1a−x+1a+x]\dfrac{1}{a^2-x^2} = \dfrac{1}{2a}\left[\dfrac{1}{a-x}+\dfrac{1}{a+x}\right]

Integrating:

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