(sin 78° - sin 42°) - (sin 66° + sin 6°)By applying sin rule:2 cos60° sin18° - 2 cos36° sin30°2 x 1/2 sin18° - 2 cos 36 x 1/2 sin 18° - cos 36°sin 18° - sin 54° Again,- ( sin 54° - sin 18°)- 2cos(36) sin(18)Also, we know sin(36) = 2 sin(18)cos(18)sin(18)=sin(36)/(2cos(18))thus,sin(54)−sin(18) = cos(36) sin(36) / cos(18) = cos(36) sin(36) / sin (72)sin(54)−sin(18)= cos(36) sin(36) / 2 sin(36) cos(36) = 1/2- ( sin 54° - sin 18°) = - 1/2sin(72
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