3 Answers
62If i remember correctly we have this was solved long back!
may be I am wrong
1convert to sinA
1/sinA = (sin2A + sin4A)/sin2Asin4A
(use sinA + sin B wala formula)
=> = 2sin3AcosA/2sinAcosA sin4A
cross multiplying and cancelling common terms
sin 3A = sin 4A
which is true as
A= pi/7
=> 7A = pi
=> 4A = pi-3A
take sin both sides
sin4A=sin3A
hence proved :)