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The value of sum(m=1)^ootan^(- 1)((2m)/...

The value of `sum_(m=1)^ootan^(- 1)((2m)/(m^4+m^2+2))` is

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To solve the problem, we need to evaluate the infinite sum: \[ \sum_{m=1}^{\infty} \tan^{-1}\left(\frac{2m}{m^4 + m^2 + 2}\right) \] ### Step 1: Simplify the Argument of the Inverse Tangent We start with the expression inside the inverse tangent function: \[ \tan^{-1}\left(\frac{2m}{m^4 + m^2 + 2}\right) \] We can rewrite the denominator: \[ m^4 + m^2 + 2 = m^4 + 2m^2 + 1 + 1 - m^2 = (m^2 + 1)^2 + 1 - m^2 \] ### Step 2: Factor the Denominator We can express the denominator as: \[ (m^2 + 1)^2 + 1 - m^2 = (m^2 + 1 - m)(m^2 + 1 + m) \] This gives us: \[ \tan^{-1}\left(\frac{2m}{(m^2 + 1 - m)(m^2 + 1 + m)}\right) \] ### Step 3: Use the Identity for Inverse Tangent Using the identity: \[ \tan^{-1}(a) - \tan^{-1}(b) = \tan^{-1}\left(\frac{a - b}{1 + ab} \] we can express our sum as: \[ \tan^{-1}(m^2 + m + 1) - \tan^{-1}(m^2 + 1 - m) \] ### Step 4: Write the Infinite Sum Now we can write the infinite sum: \[ \sum_{m=1}^{\infty} \left( \tan^{-1}(m^2 + m + 1) - \tan^{-1}(m^2 + 1 - m) \right) \] ### Step 5: Identify the Telescoping Nature Notice that this sum is telescoping. When we expand it, we have: - For \( m=1 \): \( \tan^{-1}(3) - \tan^{-1}(1) \) - For \( m=2 \): \( \tan^{-1}(7) - \tan^{-1}(3) \) - For \( m=3 \): \( \tan^{-1}(13) - \tan^{-1}(7) \) - And so on... ### Step 6: Evaluate the Limit As \( m \) approaches infinity, \( \tan^{-1}(m^2 + m + 1) \) approaches \( \frac{\pi}{2} \) and \( \tan^{-1}(1) \) is \( \frac{\pi}{4} \). Thus, the sum converges to: \[ \frac{\pi}{2} - \frac{\pi}{4} = \frac{\pi}{4} \] ### Final Answer The value of the infinite sum is: \[ \frac{\pi}{4} \]
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