The radius of circle N measures 17 cm. Chord GH = 30 cm. What is TS

http://s15.postimage.org/mbkdwlzxn/VHS_GMT_S2_04_16_UT_ques7.jpg

17 cm
15 cm
9 cm
8 cm

explain

In triangle NTH ,
NH^2 = NT^2 + TH^2
=> NT^2 = NH^2 - TH^2
=> NT^2 = (17)^2 - ( 15)^2
=> NT^2 = 289 -225
=> NT = √64
=> NT = 8 cm

as NS = NT + TS
=> TS = NS -NT
=> TS = 17 - 8
=> TS = 9 cm

so TS is 9 cm