x ∈ (0; π/2)
cos x = [tex] \frac{2}{3} [/tex]
[tex]sin^2x + cos^2x = 1[/tex]
[tex]sin^2x = 1- cos^2x[/tex]
[tex]sin^2x = 1 - \frac{2^2}{3^2} [/tex]
[tex]sin ^2x= \frac{5}{9} [/tex]
sin x = +- [tex] \sqrt{ \frac{5}{9} } [/tex]
x ∈ (0, pi/2)
------------
=> sin x = [tex] \sqrt{ \frac{5}{9} } [/tex]
