True polar>rectangular for the HP35s. Enter the following into the equation library ((SIN(REGX)*REGY)*(1@90))+((COS(REGX)*REGY)*(1i0))
Note 1@90 is polar right shift [i].
Simply enter distance (magnitude) in Y-reg and direction in X-reg. Manipulate direction with HMS> and azimuth/bearing as needed(the missing link on the 35s). Queue up the equation and [ENTER]. Whallah! You have Cartesian coordinates in complex format. [ABS] and [ARG] will decompose into polar units on the HP hemispherical angle system. Give it a whirl!