Explicație pas cu pas:
[tex]\cos^{2} (x) ={( \frac{3}{5} )}^{2} = \frac{9}{25} \\ \sin^{2} (x) + \cos^{2} (x) = 1 \\ = > \sin^{2} (x) = 1 - \cos^{2} (x) = 1 - \frac{9}{25} = \frac{16}{25} \\ 0 < x < \frac{\pi}{2} = > \sin(x) = \frac{4}{5} \\ \tan(x) = \frac{ \sin(x) }{ \cos(x) } = \frac{ \frac{4}{5} }{ \frac{3}{5} } = > \tan(x) = \frac{4}{3} [/tex]
q.e.d.
