11.8 Find the area of the figure defined on the coordinate plane by the inequality .
Solution
Answer: .
!
Solution. It is obvious that the figure
is symmetric with respect to the coordinate axes and the origin (since the inequality does not change when the signs of are changed). Therefore, it is sufficient to consider the part of the figure in the first quadrant and multiply the area of this part by 4. For non-negative , the inequality can be written as . Thus, in the first quadrant, we have a part of a circle with radius and center at (see the figure). This part of the circle is a segment with a central angle of (this is the angle between the two radii drawn to the boundary points and of this segment). Therefore, the area of the segment is , and the area of the figure is
.
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