Question

Find the value of cos40+cos80+cos160+cos240

Answer 1

Hello dear user!!! ✌️✌️


Here is your answer goes like this :


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Your question :

Find the value of cos40+cos80+cos160+cos240.....



Answer :


cos40°+cos80°+cos160°+cos240°


=2cos(40°+80°)/2cos(40°-80°)/2+cos(180°-20°)+cos(180°+60°)


[∵, cosC+cosD=2cos(C+D)/2cos(C-D)/2]


=2cos60°cos20°+cos{(90°×2)-20°}+cos{(90°×2)+60°}


=2×1/2cos20°+(-cos20°)+(-cos60°) 


[∵, cos60°=1/2, cos(180°-A)=-cosA, cos(180°+A)=-cosA]


=cos20°-cos20°-1/2

=-1/2


The answer has been explained......


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Answer 2

520 is the answer i thank mark me as brainliest