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If A+B+C=pi, then cos 2A+cos 2B+cos 2C=...

If `A+B+C=pi`, then cos 2A+cos 2B+cos 2C=

A

1) 1+4 cosA cosB sinC

B

2) -1+4 sinA sinB cosC

C

3) -1-4 cosA cosB cosC

D

4) 1+4 sinA sinB sinC

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