Question

ctg x = 4/3
tg2x = ?
x apartine cadranului III

Answer 1

Avem urmatoarea formula a tangentei unghiului dublu:

$tg2x=\frac{2tgx}{1-tg^2x}$

Stim ca:

$ctgx=\frac{1}{tgx}$

$tgx=\frac{3}{4}$

$tg2x=\frac{2\times \frac{3}{4} }{1-(\frac{3}{4})^2 }\\\\tg2x=\frac{\frac{3}{2} }{1-\frac{9}{16} } =\frac{3}{2}\times \frac{16}{7} =\frac{24}{7}$