Identities for atan(a+b) or atan(a*b)

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There are no well-known identities for the inverse tangent of a sum or product, unlike the established identities for regular trigonometric functions. The discussion highlights the lack of expansions for inverse trigonometric functions, specifically for atan(a+b) or atan(a*b). The original poster expresses frustration over the difficulty in finding useful information online. The inquiry remains open for any potential applications or needs for such identities. Overall, the consensus is that these identities are not readily available or established in mathematical literature.
rhz
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Hi,

Does anyone know of any nice identities for the inverse or arc tangent of a sum or a product?

Thanks,

rhz
 
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Any ideas out there? I searched for this on google and came up with nothing.

Thanks!
 
I don't believe there are any nice expansions for the sum or product of inverse trigs, such as how there are for trigs. What do you need them for exactly?
 

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