Sum of two inverse tangent functions

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SUMMARY

The discussion confirms that the sum of the inverse tangent functions, specifically $\tan^{-1}\frac{1}{2} + \tan^{-1}\frac{1}{3}$, equals $\frac{\pi}{4}$. This conclusion is derived by analyzing the product of complex numbers, specifically $z = (2+i)(3+i)$. The mathematical proof demonstrates the efficiency of using complex numbers in trigonometric identities.

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By considering the product of complex numbers:

$$z = (2+i)(3+i)$$

Show that

$$\tan^{-1}\frac{1}{2} + \tan^{-1}\frac{1}{3} = \frac{\pi}{4}$$
 
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$$(2+i)(3+i) = 5+5i = \sqrt{50}e^{i \arctan (1)} = \sqrt{50}e^{i \frac{\pi}{4}}$$

$$ (2+i)(3+i) = \sqrt{5} e^{i \arctan (\frac{1}{2})} \sqrt{10} e^{i \arctan (\frac{1}{3})} = \sqrt{50} e^{i [\arctan (\frac{1}{2}) + i \arctan(\frac{1}{3})]}$$

Therefore,

$$ \frac{\pi}{4} = \arctan \left( \frac{1}{2}\right) + \arctan \left(\frac{1}{3} \right)$$
 
Random Variable said:
$$(2+i)(3+i) = 5+5i = \sqrt{50}e^{i \arctan (1)} = \sqrt{50}e^{i \frac{\pi}{4}}$$

$$ (2+i)(3+i) = \sqrt{5} e^{i \arctan (\frac{1}{2})} \sqrt{10} e^{i \arctan (\frac{1}{3})} = \sqrt{50} e^{i [\arctan (\frac{1}{2}) + i \arctan(\frac{1}{3})]}$$

Therefore,

$$ \frac{\pi}{4} = \arctan \left( \frac{1}{2}\right) + \arctan \left(\frac{1}{3} \right)$$

Very efficient! But then, I'd expect nothing less from you. (Yes)
 

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