sin²6x + 8sin²3x = 0
(2sin3xcos3x)² + 8sin²3x = 0
4sin²3xcos²3x + 8sin²3x = 0
4sin²3x(cos²3x + 2) = 0
sin²6x + 8sin²3x = 0
(2sin3xcos3x)² + 8sin²3x = 0
4sin²3xcos²3x + 8sin²3x = 0
4sin²3x(cos²3x + 2) = 0