Question

Chord AC = 30 and OB = 8 below. What is the length of the radius in circle O?

Answer 1

we see that OB is perpendicular to AC (Since OBC = 90).

So if a perpendicular line is drawn from centre to a chord AC, what would probably happen to chord AC ?

Answer 2

haha nope.

The theorem is - "A perpendicular line drawn from the centre to any chord will BISECT the chord".

Hence chord AC gets bisected. So basically B becomes mid point of AC,

Hence AC = AB = 15 cm.

So AB = 15 and OB = 8. all u now have to do is use the pythagoras theorem to find the radius,.