A chord is 2cm from the centre of a circle. If the radius of the circle is 5cm, find the length of the chord
-
A.
2(sqrt{21})cm -
B.
(sqrt{42})cm -
C.
2(sqrt{19})cm -
D.
(sqrt{21})cm
Correct Answer: Option A
Explanation
From (bigtriangleup) OMQ find /MQ/ by Pythagoras OQ2 = OM2 + MQ2
52 = 22 + MQ2
25 = 4 + MQ2
25 – 4 = MQ2
21 – MQ2
MQ2 = 21
MQ2 = (sqrt{21})
Length of chord = 2 x (sqrt{21}) = 2(sqrt{21})cm