Inverse trig equation

1. The problem statement, all variables and given/known data

I have knocked a problem down to:

[tex]-arcsec \frac{3x}{4}[/tex]

but my textbook gives the answer as:

[tex]arctan \frac{4}{\sqrt{9x^2 - 16}}[/tex]

Are these somehow equivalent?


2. Relevant equations

3. The attempt at a solution
I don't think so. However, I get arccsc (3x/4) being equal to arctan(4/sqrt(9x^2 - 16))

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