Kąt α jest ostry i sinα= 8/9. Wtedy cosα jest równy

$\displaystyle \frac{1}{9}$\displaystyle \frac{1}{9}

$\displaystyle \frac{8}{9}$\displaystyle \frac{8}{9}

$\displaystyle \frac{\sqrt{17}}{9}$\displaystyle \frac{\sqrt{17}}{9}

$\displaystyle \frac{\sqrt{65}}{9}$\displaystyle \frac{\sqrt{65}}{9}