sin780 sin480 +cos120sin150=1/2
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sin (720+60) = sin 720 cos 60 + cos 720 sin 60 = 0 + sin60 = √3 / 2
sin (480) = sin (360 +120) = sin 360 cos 120 + cos 360 sin 120 = 0 + sin 120 = sin (90+30) = cos 30 = √3 / 2
cos (120) = cos (90+30) = - sin 30 = -1/2
sin (150) = sin (180-30) = sin 180 cos 30 - cos 180 sin 30 = 0 - (-sin30) = sin 30 = 1/2
(√3/2)² -1/4 = 3/4-1/4 = 1/2
sin (A+B) = sin A Cos B + cos A sin B
cos (A+B) = cos A cos B - sin A sin B
sin (480) = sin (360 +120) = sin 360 cos 120 + cos 360 sin 120 = 0 + sin 120 = sin (90+30) = cos 30 = √3 / 2
cos (120) = cos (90+30) = - sin 30 = -1/2
sin (150) = sin (180-30) = sin 180 cos 30 - cos 180 sin 30 = 0 - (-sin30) = sin 30 = 1/2
(√3/2)² -1/4 = 3/4-1/4 = 1/2
sin (A+B) = sin A Cos B + cos A sin B
cos (A+B) = cos A cos B - sin A sin B
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