OEWe need to find the area of the circle cantered at O in the figure given.
Attachment:
GRE circle 5.jpg [ 26.31 KiB | Viewed 1303 times ]
If we join OC, then we can see that OC is the radius of the circle.
Also, we know that radius of a circle is perpendicular to the tangent.
Hence OC, radius of circle, is perpendicular to AB and is also
the height of equilateral triangle OAB.
We know,
Height of equilateral triangle = √3/2 ∗ 𝑠𝑖𝑑𝑒
Side of equilateral triangle OAB is given as 10cm.
OC = √3/2 × 10 = 5√3
Hence,
Area of circle = 𝜋(5√3)^2= 75 𝜋
Ans. (C)