From an external point Q, the length of the tangent to a circle is 5 cm and the distance of Q from the centre is 8 cm. The radius of the circle is
Option: 1 39 cm
Option: 2 3 cm
Option: 3
Option: 4 7 cm
?????? ???????????? ????? ????, ?? ???? ????? ????.??? ???????? 16 ??? ?????.?????? 1?? 12 ???.?????? ?????.????? ?????? ???????? ??? ???????? ?????????? ???????????? ??? ??? ????.?????? 5 ?????? ??? 5???? ??? .......8 ?????? ??? 8???? ??? ......???? ????