Question

Cum se rezolva sin(a/2) daca sin(a)=5/13?

Answer 1

$sin \frac{a}{2}= \sqrt{ \frac{1-cosa}{2} } \\ cosa= \sqrt{1-sin^2a}= \sqrt{1-( \frac{5}{13})^2 } = \frac{12}{13} \\ sin \frac{a}{2}= \sqrt{ \frac{1- \frac{12}{13} }{2} } = \sqrt{ \frac{1}{26} }$