Question
sin 20∘sin 40∘sin 60∘sin 80∘=
Answer: Option C
:
C
sin20osin40∘sin60∘sin80∘
=12sin20∘sin60∘(2sin40∘sin80∘)
=12sin20∘sin60∘(cos40∘−cos120∘)
=12.√32sin20∘(1−2sin220∘+12)
=√34sin20∘(32−2sin220∘)
=√38(3sin20∘−4sin320∘)
=√38sin60∘=√38.√32=316
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:
C
sin20osin40∘sin60∘sin80∘
=12sin20∘sin60∘(2sin40∘sin80∘)
=12sin20∘sin60∘(cos40∘−cos120∘)
=12.√32sin20∘(1−2sin220∘+12)
=√34sin20∘(32−2sin220∘)
=√38(3sin20∘−4sin320∘)
=√38sin60∘=√38.√32=316
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