Answer
$\sqrt 2$
Work Step by Step
To find out exact value of $ \sec 45^{\circ}$, considering special triangle- $ 45^{\circ} - 45^{\circ} - 90^{\circ}$
$\sec 45^{\circ}$ = $\frac{hypotenuse}{side - adjacent - 45^{\circ}}$
$\sec 45^{\circ}$ = $ \frac{\sqrt 2}{1}$
= $\sqrt 2$
