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Vector Algebra

Question
CBSEENMA12032716

Using the method of integration find the area bounded by the curve |x| + |y| = 1.
[Hint: The required region is bounded by lines x + y = 1, x– y = 1, – x + y = 1 and
– x – y = 1].


Solution

The given curve is
|x| + |y| = 1
or ± x ± y = 1
The given equation represents four lines
x + y = 1, x - y = 1,
- x + y = 1 and -x - y = 1
which enclose a square of diagonal 2 units length.
 

Required area is symmetrical in all the four quadrants.
∴     required area = 4 (area OAB)
equals space 4 space integral subscript 0 superscript 1 left parenthesis 1 minus straight x right parenthesis space dx space equals space 4 space open square brackets straight x minus straight x squared over 2 close square brackets subscript 0 superscript 1 space equals space 4 open square brackets open parentheses 1 minus 1 half close parentheses minus left parenthesis 0 minus 0 right parenthesis close square brackets
equals space 4 space cross times space 1 half space equals space 2 space sq. space units. space

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