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If A+B+C=pi, then cos B+cos C=...

If `A+B+C=pi`, then `cos B+cos C=`

A

`2 cos (A)/(2) cos (B-C)/(2)`

B

`2 sin (A)/(2) cos (B-C)/(2)`

C

`2 cos (C)/(2) cos (A-B)/(2)`

D

`2 cos (B)/(2) cos (C)/(2)`

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HIMALAYA PUBLICATION-MEASUREMENT OF ANGLES, TRIGONOMETRIC RATIOS AND RELATION BETWEEN SIDES AND ANGLES OF A TRIANGLE-QUESTION BANK
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