cos1°+cos2°+cos3°+·······+cos180° is equal to
1
0
2
-1
Explanation for correct option:
Simplifying the series by Trigonometric identities:
Here, we use cos(π-θ)=-cosθ
cos1°+cos2°+cos3°+·······+cos180°=cos1°+cos2°+cos3°+·····+cos90°+·····+cos177°+cos178°+cos179°+cos180°=cos1°+cos2°+cos3°+·····+cos90°+·····+cos177°+cos178°+cos179°+cos180°=cos1°+cos2°+cos3°+·····+cos90°+·····+cos180°-3°+cos180°-2°+cos180°-1°+cos180°=cos1°+cos2°+cos3°+·····+cos90°+·····-cos1°-cos2°-cos1°+cos180°=cos90°+cos180°=0-1=-1
Therefore, Option (D) is correct.
-41--51 is equal to