一个球的直径是6cm,距球心2cm处有一截面圆,这个截面圆的半径是()
①
img class=kfformula src=zzximg/20190809/1565323084593264.png data-latex=4\sqrt {2}/
②
img class=kfformula src=zzximg/20190809/1565323084828913.png data-latex=\sqrt {5}/
③
img class=kfformula src=zzximg/20190809/1565323084235099.png data-latex=1/
④
img class=kfformula src=zzximg/20190809/1565323084316280.png data-latex=\sqrt {13}/