Question

Find value of cos 55 +cos 125+ cos 300

Answer 1

Hi ,

Here we use Signs of Trigonometric

Ratios if θ lies in I , II , III , IV

quandrants.

According to the problem given,

Cos 55 + Cos 125 + Cos 300

= Cos ( 90 - 35) + Cos ( 90 + 35 ) +

Cos ( 270 + 30 )

= Sin 35 - Sin 35 + Sin 30

= Sin 30

= 1/2

I hope this helps you.

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Answer 2

Cos 55+ cos 125+ cos 300

= cos(90-35)+ cos (90+35)+ cos (360-60)

= sin 35 -sin 35 + cos 60

= cos 60 = 1/2

Hope it helps