2 circles of the same radius are on a 2-D plane that exists such that ...
In the above figure, we need to find the Area of BO'CO
Since B and C are on the circumference of the circle, BO=CO=BO'=CO' =r . Also OO' =r
We can say that BOO' and COO' are 2 equilateral triangles with sides r
Thus area of BO'CO = area BOO' + area COO'
Thus area of BO'CO
Area of 1 circle = πr
2Ratio =
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2 circles of the same radius are on a 2-D plane that exists such that ...
Let the radius of the circles be $r$.
Since the center of one circle lies on the circumference of the other circle, the distance between the centers of the circles is also $r$.
Let $O_1$ and $O_2$ be the centers of the circles, and let $A$ and $B$ be the points where the circles intersect. Let $C$ be the intersection of $O_1O_2$ and $AB$.
[asy] unitsize(2cm); pair O1,O2,A,B,C; O1 = (0,0); O2 = (1,0); A = intersectionpoints(Circle(O1,1),Circle(O2,1))[0]; B = intersectionpoints(Circle(O1,1),Circle(O2,1))[1]; C = extension(O1,O2,A,B); draw(Circle(O1,1)); draw(Circle(O2,1)); draw(O1--A--B--O2--cycle); dot(O1); dot(O2); dot(A); dot(B); dot(C); label("$O_1$",O1,W); label("$O_2$",O2,E); label("$A$",A,NW); label("$B$",B,NE); label("$C$",C,S); [/asy]
$\triangle O_1O_2C$ is an isosceles triangle with $O_1O_2 = O_1C = O_2C = r$.
Since $\angle O_1O_2C = \angle O_1CO_2 = \angle O_2CO_1 = 90^\circ$, $\triangle O_1O_2C$ is an isosceles right triangle.
Therefore, $\angle O_1OC = \frac{1}{2} \cdot 90^\circ = 45^\circ$.
The area of the sector $AO_1B$ is $\frac{1}{8}$ of the area of the circle centered at $O_1$, because $\angle AOB = \frac{1}{2} \cdot 45^\circ = 22.5^\circ$, so the area of sector $AO_1B$ is $\frac{22.5^\circ}{360^\circ} = \frac{1}{8}$ of the total circle.
The area of triangle $CO_1O_2$ is $\frac{1}{2} \cdot O_1O_2 \cdot O_1C = \frac{1}{2} \cdot r \cdot r = \frac{1}{2}r^2$.
Therefore, the area of quadrilateral $ACOB$ is $\frac{1}{8}$ of the area of the circle plus $\frac{1}{2}r^2$.
The area of the circle is $\pi r^2$.
Therefore, the ratio of the area of quadrilateral $ACOB$ to the area of the circle is $\frac{\frac{1}{8}\pi r^2 + \frac{1}{2}r^2}{\pi r^2} = \boxed{\frac{2}{\pi}+ \frac{1}{4}}$.
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