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The value of sin 78^@ - sin 66^@ - sin ...

The value of `sin 78^@ - sin 66^@ - sin 42^@ + sin 6^@` is

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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