Question

5) No triangulo retângulo, temos cos a = 12/13, então o sen a será:
a) 13/12
b) 13/5
c) 5/13
d) 5/12
​

Answer 1

${sen \alpha }^{2} + {( \frac{12}{13} )}^{2} = 1 \\ {sen \alpha }^{2} = 1 - \frac{144}{169} \\ {sen \alpha }^{2} = \frac{169 - 144}{169} \\ {sen \alpha }^{2} = \frac{25}{169} \\ {sen \alpha } = \sqrt{ \frac{25}{169} } = \frac{5}{13}$

alternativa c