Section 6: Functions91
Keystrokes Display
g FIX 6
 62.3651
FIX 6 display lets you see the whole number.
g FIX 4
 62.3651
Display set to FIX 4.
USER
 62.3651

g CLX
 0

In the HP-41C, trigonometric functions assume angles in decimal degrees, decimal radians, of decimal grads. If you want to use any trigonometric functions on angles given in degrees, minutes, 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 great circle distance that Odysseus must sail in order to court her.

 Distance = cos –1 [ sin (LATs) sin (LATd) + cos (LATs) cos (LATd) cos (LNGd – LNGs)] × 60
Where:
 LATs and LNGs = latitude and longitude of the source (Tristan da Cunha). LATd and LNGd = latitude and longitude of the destination (St. Helena).
Solution: Convert all degrees, minutes, seconds entries into decimal degrees as you key them in. The equation for the great circle distance from Tristan da Cunha to the nearest inhabited land is:
 Distance = cos –1 [ sin (37° 03′) sin (15° 55′) + cos (37° 03′) cos (15° 55′) cos (5° 43′W – 12° 18′W)] × 60
Since the HR function is still assigned to the ex key location, simply switch to USER mode.