Let O is centre of big circle, and O′ is centre of smaller circle. Both are touch internally each other. OA=6cmO′A=4cm Here PR is longest chord of big circle P.S=
PR
2
OS=AS−OA =8−6=2cm In ΔPSO (PS)2+(OS)2=(OP)2 ⇒ (PS)2+(2)2=(6)2 PS=√36−4=√32=4√2 Now, PS=