Anyone good with trig that can help?

[synx]

I have to prove arcsec(x) = arccos(1/x) , I have no idea where to start and after reading over trig identities nothing is making sense. Can anyone assist me with just getting a start on it?

 

[stapel]

Have you tried drawing a right triangle with angle ß such that sec(ß) = x/1?

Eliz.