prove that cot 35+cot 85+cot 155=0
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Answer:
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Step-by-step explanation:
Correct Question :-
cos35° + cos85° + cos155° = 0
Solution :-
Taking L.H.S :-
= cos35° + cos85° + cos155°
We can write,
35° as :- 60°-25°
85° as :- 60° + 25°
= cos(60°-25°) + cos(60°+25°) + cos155°
We know that :-
cos(A+B)+cos(A-B) = 2cosAcosB
= (2cos60°cos25°) + cos155°
= (2 cos25°) + cos155°
= cos25° + cos155°
We know that :-
= 0
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