## Precalculus (6th Edition)

$72^\circ 47'$
In this kind of subtraction, we subtract the degrees from the degrees and the minutes from the minutes: $90^\circ$ can be rewritten as: $89^\circ 60'$ $89^\circ 60'-17^\circ 13'=(89-17)^\circ+(60-13)'=72^\circ 47'$