Question

sin^2π/18 + sin^2π/9 + sin ^2 7π/18 +sin^24π/9

Answer 1

sin2pi/18 + sin2pi/9 + sin2 7pi/18 + sin24pi/9 

=sin2pi/18 + sin27pi/18 + sin2 (pi/2-7pi/18) + sin2(pi/2-pi/18)

=sin2pi/18+ cos2pi/18 + sin27pi/18 + cos27pi/18

 1 +1

= 2

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