- Home
- Standard 11
- Mathematics
9.Straight Line
medium
The area enclosed within the curve $|x| + |y| = 1$ is
A
$\sqrt 2 $
B
$1$
C
$\sqrt 3 $
D
$2$
(IIT-1981)
Solution
(d) The given lines are $ \pm x \pm y = 1$
i.e. $x + y = 1,x – y = 1,x + y = – 1$and $x – y = – 1$
These lines form a quadrilateral whose vertices are $A( – 1,0),B(0, – 1),C(1,0)$and $D(0,1)$
Obviously $ABCD$ is a square.
Length of each side of this square is $\sqrt {{1^2} + {1^2}} = \sqrt 2 $
Hence area of square is $\sqrt 2 \times \sqrt 2 = 2sq.$units
Trick: Requird area = $\frac{{2{c^2}}}{{|ab|}} = \frac{{2 \times {1^2}}}{{|1 \times 1|}} = 2$.
Standard 11
Mathematics