Question

plz solve this problem?
thanks in advance

Answer 1

cos24+cos55+cos(180-55)+cos(180+24)+cos(360-60)
cos24+cos55-cos55-cos24+cos60
=cos60
=1/2

Answer 2

Solution :

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Given & To Find :

cos 24° + cos 55° + cos 125° + cos 204° + cos 300° = ?

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As we know that,

cos (180 + x) = - cosx,


cos (360 - y) = cos y,

&

cos (90 + y) =- sin y          (As sin (90 - A) = cos A)

So,

⇒ cos 24° + cos 55°+ cos 125° + cos 204° + cos 300°

⇒ cos 24° + cos 55° + cos (90 + 35)° + cos (180 + 24)° + cos (360 - 60)°

⇒ cos 24° + cos 55° +(- sin 35°) + (- cos 24°) + (- cos 60°)

⇒ cos 24° + cos 55° - (sin 35° + cos 24°)  + cos 60°

⇒ cos 60° = $\frac{1}{2}$

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                                  Hope it Helps !!

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