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\sin 150^{\circ} \cos 120^{\circ}+\cos 330^{\circ} \sin 660^{\circ}+1=0 |
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Answer» L.H.S.sin150 cos 120 + cos 330 sin 660 +1=sin (180-30) cos (180-60) +cos (360- 30) sin ( 2×360 -60) +1=sin 30 [ - cos60 ] + cos 30 [ - sin 60] +1=1/2 ( - 1/2) + root3 /2 ( - root3 /2) +1=-1/4 + (- 3/4) +1=-1/4 -3/4 +1 =(-1-3)/4 +1= -1 +1= 0 |
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