HSC Ext 1 Math Australia trigonometry question
Prove that $\sin^2(\pi/18)+\sin^2(5\pi/18)+\sin^2(25\pi/18)=3/2$.
I believe the way im meant to solve this involves mainly the use of tried identities, and I have a strong feeling the triple angle identities have a part. Also this is a band 4 question worth 3 marks
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