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Prove that, cos24° + cos55° +cos125° + cos204°+ cos300°=$\frac{1}{2}$

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Prove that, cos24° + cos55° +cos125° + cos204°+ cos300°=$\frac{1}{2}$

Solution:

L.H.S:

cos24° + cos55° +cos125° + cos204°+ cos300°

= cos24° + cos55° +cos125° + cos(180°+24°)+ cos(360°-60°)

= cos24° + cos55° + cos125°-cos24°+cos60°

= cos55+cos(180°-55°) + $\frac{1}{2}$

= cos 55° –cos55° + $\frac{1}{2}$

= $\frac{1}{2}$ 

= R.H.S [Proved]

আরও দেখুন

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