So by the trigonometric identities, $\displaystyle \sec \theta = \frac {1} {\cos \theta}$, but according to my calculator, $\displaystyle \sec 0 = 1.57$, and $\displaystyle \cos 0 = 1$. how can this be, seeing as $\displaystyle \frac {1} {1} = 1.57$ isnt true??