sinē(1°)+sinē(2°)+···+sinē(88°)+sinē(89°) =
Put some terms in the middle:
sinē(1°)+sinē(2°)+···+sinē(44°)+sinē(45°)+sinē(46°)+···+sinē(88°)+sinē(89°)
sinē(1°)+sinē(2°)+···+sinē(44°)+sinē(45°)+sinē(90°-44°)+···+sinē(90°-2°)+sinē(90°-1°)
Use the fact that sin(90°-q) = cos(q)
sinē(1°)+sinē(2°)+···+sinē(44°)+sinē(45°)+cosē(44°)+···+cosē(2°)+cosē(1°) =
Rearrange the terms putting the
1st and 89th terms together,
2nd and 88th terms together,
···
44th and 46th terms together:
[sinē(1°)+cosē(1°)]+[sinē(2°)+cosē(2°)]+···+[sinē(44°)+cosē(44°)]+sinē(45°) =
Use the fact that sinē(q)+cosē(q) = 1
1 + 1 + ··· + 1 + sinē(45°), where there are 44 1's.
44 + sinē(45°) =
44 + =
44 + =
44 + =
44.5
Edwin