Students use interactive content to investigate the six trigonometric functions: sine, cosine, tangent, secant, cosecant, cotangent, including relationships between each. The unit circle animation helps build the relationships, which they derive and prove. The second stage of the investigation has students building relationships for double angle formulas, thanks to a series of visual prompts. The Word document can be edited to suit your needs, so too the companion TI-Nspire file.