If the length of a chord, drawn at a distance of 21 cm from the centre of a circle, is 40 cm, then the radius (in cm) of the circle is:
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e. 29.
We know that,
The perpendicular drawn from the center of the chord bisects the chord in two equal parts
Applying Pythagoras' theorem in triangle AOD
OD2 = AO2 + AD2
Now, according to the question
OD2 = AO2 + AD2
⇒ OD2 = 212 + 202
⇒ OD2 = 441 + 400
⇒ OD2 = 841
⇒ OD = √841
⇒ OD = 29
Hence, the radius of the circle is 29 cm