sin20 sin 40 sin60 sin 80
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=> sinA sin(60°-A) sin(60°+A) = 1/4 sin3A
so
sin60°[ sin20° sin40° sin 80°]
= sin60°[ sin20° sin(60°-20°) sin(60°+20°)]
= sin60°×1/4× sin(3×20°)
=√3/2×1/4×√3/2
= 3/16
so
sin60°[ sin20° sin40° sin 80°]
= sin60°[ sin20° sin(60°-20°) sin(60°+20°)]
= sin60°×1/4× sin(3×20°)
=√3/2×1/4×√3/2
= 3/16
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