Question 1199182
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Consider this shaded area in red
*[illustration Screenshot_193a.png]
The angle DOF is 60 degrees as the other tutors have pointed out.
This means the red shaded pizza slice area is 60/360 = 1/6 of a full circle's area of radius 2.


full circle area = {{{pi*r^2 = pi*2^2 = 4pi}}}
1/6 of that full area = {{{(1/6)*4pi = 2pi/3}}}


The area of the red shaded region shown above is {{{2pi/3}}} square cm.


Then subtract off the area of triangle DOF
{{{(2pi)/3 - sqrt(3)/2}}}
This represents the blue shaded region below
*[illustration Screenshot_194a.png]


Quadruple this result since there are 4 identical symmetric (i.e. mirrored) such regions
{{{4*( (2pi)/3 - sqrt(3)/2 )}}}


{{{8pi/3 - 2*sqrt(3)}}}


Then subtract this from the full circle area 
{{{4pi - (8pi/3 - 2*sqrt(3))}}}


{{{4pi - 8pi/3 + 2*sqrt(3)}}}


{{{12pi/3 - 8pi/3 + 2*sqrt(3)}}}


{{{4pi/3 + 2*sqrt(3)}}}
That is the area between the vertical lines. 
It is the area of region ABCD.
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