Two circles of radius of 6 cm each. They intersect each other such that each passes through the centre of the other. What is the length of the common chord?
Answer & explanation
Correct answer: option 3

⇒ Let the centres be at A and B respectively.
Here, AC = CB = BD = DA = radius of circles = 6cm
CD is the common chord
Since they intersect each other such that each passes through the centre of the other, AB = 6 cm,
Hence, triangle ACB is an equilateral triangle whose AC = CB = AB = 6cm,
According to the concept,
CE is the height of triangle ACB
So, CE = \(\frac{√3}{2}\) x 6 = 3\(\sqrt {3 }\) cm,
Similarily, DE = 3\(\sqrt {3 }\) cm,
Now, CD = 3\(\sqrt {3 }\) + 3\(\sqrt {3 }\) = 6\(\sqrt {3 }\) cm
Therefore, the length of common chord is 6\(\sqrt {3 }\).