Relazione fondamentale della goniometria
\[sen^{2}\alpha +cos^{2}\alpha =1,\, \, \, \, \forall \alpha \in R\]
Formule inverse
\[sen\alpha=\pm \sqrt{1-cos^{2}\alpha },\, \, \, \, \, \, cos\alpha=\pm \sqrt{1-sen^{2}\alpha }\]
\[sen^{2}\alpha =1-cos^{2}\alpha,\, \, \, \, \, cos^{2}\alpha =1-sen^{2}\alpha\]
Altre relazioni della goniometria
\[tan\alpha =\frac{sen\alpha }{cos\alpha },\, \, \, \, \, cot\alpha =\frac{cos\alpha }{sen\alpha }\]
\[tan\alpha \cdot cot\alpha =1\]
\[tan\alpha=\frac{1}{cot\alpha},\, \, \, cot\alpha=\frac{1}{tan\alpha}\]
\[sec\alpha =\frac{1}{cos\alpha},\, \, \, \, cosec\alpha =\frac{1}{sen\alpha}\]