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In a DeltaABC, a ^(2) cos 2B+b^(2) cos 2...

In a `DeltaABC, a ^(2) cos 2B+b^(2) cos 2A+2ab cos (A-B)=`

A

`a^(2)`

B

`c ^(2)`

C

`b ^(2)`

D

`a ^(2)+ b ^(2)`

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