Avem urmatoarea formula a tangentei unghiului dublu:
[tex]tg2x=\frac{2tgx}{1-tg^2x}[/tex]
Stim ca:
[tex]ctgx=\frac{1}{tgx}[/tex]
[tex]tgx=\frac{3}{4}[/tex]
[tex]tg2x=\frac{2\times \frac{3}{4} }{1-(\frac{3}{4})^2 }\\\\tg2x=\frac{\frac{3}{2} }{1-\frac{9}{16} } =\frac{3}{2}\times \frac{16}{7} =\frac{24}{7}[/tex]
