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IF A + B + C = pi then cos ^2 A +...

IF ` A + B + C = pi` then ` cos ^2 A + cos^2 B + cos^2 C=`

A

` 1- cos A cos B cos C`

B

` 1- 2 cos A cos B cos C `

C

`2 cos A cos B cos C `

D

`1+ cos A cos B cos C `

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B
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