Reflector 72 comprises a parabolic arc of which the focus is at 76 and the directrix is at 77, {HEAD ~ the axis} 79 of {TAIL ~ the parabola} being horizontal 
of
Reflector 72 comprises a parabolic arc of which the focus is at 76 and the directrix is at 77 , { HEAD ~ the axis } 79 of { TAIL ~ the parabola } being horizontal
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH