Answer
$\sec$ 39$^{\circ}$ = $\csc$ 51$^{\circ}$
Work Step by Step
According to the Cofunction Identities
$\sec$ $A$ = $\csc$ (90$^{\circ}$ - $A$)
Therefore:
$\sec$ 39$^{\circ}$ = $\csc$ (90$^{\circ}$ - 39$^{\circ}$)
= $\csc$ 51$^{\circ}$
Therefore:
$\sec$ 39$^{\circ}$ = $\csc$ 51$^{\circ}$