HP -67 Owner's Handbook Manual page 101

Function Keys 97
Example: Subtract 142.78° from 312°32'17", with the answer in
degrees, minutes, seconds format.
Press Display
312.3217
FIX 6 from previous
example.
142.78 142.78 Decimal degrees.
a To degrees, minutes,
seconds.
CHS Angle made negative.
0 This is 169°4529".
[DsP ¥ Display mode reset to
FIX 2.
In the HP-67, trigonometric functions assume angles in decimal
degrees, decimal radians, or decimal grads, so if you want to compute
any trigonometric functions of an angle given in degrees, minutes,
and seconds, you must first convert the angle to decimal degrees.
Example: Lovesick sailor Oscar
Odysseus dwells on the island of
Tristan da Cunha (37°03'S, 12°18'W),
and his sweetheart, Penelope, lives on
the nearest island. Unfortunately for
the course of true love, however,
Tristan da Cunha is the most isolated
inhabited spot in the world. If Penelope
lives on the island of St. Helena
(15°55'S, 5°43'W), use the following
formula to calculate the greatcircle distance that Odysseus mustsail
in order to court her.
Distance = cos™! [sin (LAT;) sin (LATy) + cos (LAT;) cos (LATy)
cos (LNGy — LNGy)| X 60.
Where LAT, and LNG, = latitude and longitude of the source
(Tristan da Cunha).
LAT4 and LNG, =latitude and longitude of the destination.