- #1
Char. Limit
Gold Member
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Homework Statement
I was reading on the Weierstrass substitution, and I came across the following trigonometric identity:
[tex]tan^{-1}(\alpha) - tan^{-1}(\beta) = tan^{-1}\left(\frac{\alpha-\beta}{1+\alpha \beta}\right)[/tex]
Homework Equations
I'm not really sure which equations are applicable here.
The Attempt at a Solution
What my question is is "how is this proven?". And try as I might, I don't see a way to prove this. Any help would be deeply appreciated.