Question

The value of cos 35+cos85+cos155 is​

Answer 1

Step-by-step explanation:

Cos 35°+cos85°+cos155°

= 2cos{(35°+85°)/2}cos{(35°-85°)/2}+cos(180°-25°) 

[cosC+cosD=2cos{(C+D)/2}cos{(C-D)/2}]

=2cos(120°/2)cos(50°/2)+cos{(90°×2)-25°}

=2cos60°cos25°+(-cos25°)

=2×(1/2)cos25°-cos25°

=0 (Proved)

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Answer 2

Answer:

cos 35tita35+costita85++cos155is0

cos35+cos85+cos155

2cos60+2cos25 =0

proved

answer is

0

Step-by-step explanation:

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