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Evaluate sin78^(@)-sin66^(@)-sin42^(@)+s...

Evaluate `sin78^(@)-sin66^(@)-sin42^(@)+sin6^(@)`

Text Solution

Verified by Experts

The expression `=(sin78^(@)-sin42^(@))-(sin66^(@)-sin6^(@))=2cos(60^(@))sin(18^(@))-2cos36^(@).sin30^(@)`
`=sin18^(@)-cos36^(@)=(sqrt(5)-1)/(4) -(sqrt(5)+1)/(4)=-1/2`
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