Resposta :
sen² + cos² = 1
[tex]\frac{3^2}{5^2} + cos² = 1[/tex]
[tex]cos² = 1 - \frac{9}{25} [/tex]
[tex]cos² = \frac{16}{25} [/tex]
[tex]cos = \frac{4}{5} [/tex]
[tex]tg = \frac{sen}{cos} [/tex]
[tex]tg = \frac{\frac{3}{5}}{\frac{4}{5}} [/tex]
[tex]tg = \frac{3}{5} \cdot \frac{5}{4} = \frac{15}{20} = \frac{3}{4} [/tex]