Find the area of the closed curve bounded by these equations.

Algebra Level 1

You have four equations.

y |y| + x |x| = 1

y |y| - x |x| = 1

y |y| + x |x| = -1

y |y| - x |x| = -1

Find the area of the closed disjoint curve bounded by these equations.


The answer is 3.142.

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2 solutions

Parth Sankhe
Nov 16, 2018

The first equation, in the first quadrant, is the equation of a circle.

It is the equation of hyperbola for the 2nd and 4th quadrant. These hyperbolas stretch to infinity. (the equation isn't defined in the 3rd quadrant, (equation of an imaginary circle)).

All the other equations are just reflections of this equation in all the other quadrants, thus the overall figure of all the equations would be a circle, touching 2 hyperbolas, where one has a vertical axis and the other horizontal. The hyperbolas will never intersect, and thus would never form a closed figure.

Thus, all we have left is the circle.

Area = π (1)² = π

Vijay Simha
Nov 13, 2018

The closed curve formed by these four equations is simply the circle:

x^2 + y^2 = 1

Area of this circle is Pi....

Can you elaborate on this? How did you arrive at this conclusion?

Pi Han Goh - 2 years, 7 months ago

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It is not exactly a closed curve, it is a dis-joint circle

Vijay Simha - 2 years, 5 months ago

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