[tex]Zadanie\\\\cos\alpha=\frac{2}{7}\\\\sin^2\alpha+cos^2\alpha=1\\\\sin^2\alpha+(\frac{2}{7})^2=1\\\\sin^2\alpha+\frac{4}{49}=\frac{49}{49}\ \ \mid-\frac{4}{9}\\\\ sin^2\alpha=\frac{45}{49}\\\\sin\alpha=\sqrt{\frac{45}{49} }\\\\sin\alpha= \frac{\sqrt{9\cdot5} }{\sqrt{49} }\\\\sin\alpha=\frac{3\sqrt{5} }{7}\\\\Odp.\ D[/tex]
