Written by Dave Coffin around 1992.
XEQ D N? 42.3566 Downtown Boston E? -71.0569 Always negative in USA!! N? 21.426 Mecca, Saudi Arabia E? 39.838 5397.33132593 Distance in nautical miles x<>y 60.420494571 Compass heading (30 degrees north of east)This is counter-intuitive because, on a flat map of the world, Mecca appears far to the east and a little south of Boston. But if you find these two cities on a globe and connect them with a tight string, you can see that the shortest path goes north before it goes south.
HP 35s users must read this!!
Distance output is in nautical miles. Change line D30 to 111.12 for kilometers, or 69.046767 for statute miles.
D01 LBL D D02 DEG D03 INPUT N D04 STO X D05 INPUT E D06 INPUT N D07 1 D08 θ,r→y,x D09 INPUT E D10 R↑ D11 - D12 x<>y D13 θ,r→y,x D14 R↑ D15 x<>y D16 y,x→θ,r D17 x<>y D18 RCL- X D19 x<>y D20 θ,r→y,x D21 180 D22 R↓ D23 R↓ D24 +/- D25 y,x→θ,r D26 R↓ D27 - D28 x<>y D29 ACOS D30 60 D31 × D32 RTN HP-32SII: checksum = AAAA, length = 48.0 HP-33S: checksum = EE88, length = 132 HP-35S: checksum = EA58, length = 102