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## Homework Statement

Find the angle between the line x=7 and the catenary [tex]y=20\cosh{(\frac{x}{20})}-15[/tex]

## The Attempt at a Solution

I found the tangent has gradient [tex]\sinh{(\frac{7}{20})}[/tex]

Then I used [tex]\tan{\theta}=|\frac{1}{m}|[/tex]

where [tex]m=\sinh{(\frac{7}{20})}[/tex]

And evaluated using inverse tan on my calculator.

I'm pretty sure we aren't meant to use a calculator though, so my question is can the inverse tan of that be evaluated manually somehow?

Thanks