Reflector 74 is a parabolic arc of which the focus is also at 76, but {HEAD ~ the axis} 80 of the parabola makes with {TAIL ~ the horizontal an angle} α equal to the maximum solar altitude: the directrix of arc 74 is at 81, and makes with directrix 77 an angle equal to the supplement of angle α 
Reflector 74 is a parabolic arc of which the focus is also at 76 , but { HEAD ~ the axis } 80 of the parabola makes with { TAIL ~ the horizontal an angle } α equal to the maximum solar altitude : the directrix of arc 74 is at 81 , and makes with directrix 77 an angle equal to the supplement of angle α
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH