Give that cos 36 = ( 1 + sin 18 ) / ( 1 + 2 sin 18 )
Prove that 4 sin^2 18 + 2 sin 18 -1 = 0 by using double angle forumulae of cosine.
(b)
Hence, find the value of sin 18.
更新1:
Please use cos 36 = ( 1 + sin 18 ) / ( 1 + 2 sin 18 ) and double angle forumulae of cosine.