We are given that two tangents $
OA&OB$, of length 3 inches each, intersect at point O and form an angle of 60 degrees (Two tangents meeting at a common point outside the circle are equal in length).
As triangle $
AOC&$ triangle CBO are congruent triangles, we get angle $
AOC=$ angle $
COB=30$ degrees each. Also as radius is always perpendicular on tangent, we get angle $\mathrm{CAO}=90$ degree .
Now, using the measure of angle CAO ( $
=90$ degree) \& angle AOC ( $
=30$ degrees), in triangle ACO , we get angle $
ACO=180∘−(90∘+30∘)=180∘−120∘=60∘$
As shown in the figure to the right, in a triangle having angles $
90,60&30$, the corresponding opposite sides are $
2a,a√3&a$ respectively.
Attachment:
GRE triangle (6).png [ 44.61 KiB | Viewed 79 times ]
Using the $
90,60,30$ triangle rule, in the triangle ACO , the side opposite to 60 degrees i.e. CO is given as 3 , so we get the side opposite to 30 degrees as $
3√3=√3=AO=$ radius of the circle.
So, we get the area of the circle as $
πr2=π(√3)2=3π$
Hence the answer is (C).