Lil Bit Complex

Geometry Level 4

Find the area of region bounded by x + y + x y 4 , x 1 , y x 2 2 x + 1 |x+y|+|x-y|\leq4,|x|\leq1,y\geq\sqrt{x^2-2x+1} .

2.5 5 2 1 7.6 6 7 9.4

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1 solution

Chew-Seong Cheong
Mar 19, 2016

We note that:

{ x + y + x y 4 2 y 2 x 1 1 x 1 y x 2 2 x + 1 y 1 x \begin{cases} |x+y| + |x-y| \le 4 & \Rightarrow -2 \le y \le 2 \\ |x| \le 1 & \Rightarrow -1 \le x \le 1 \\ y \ge \sqrt{x^2 -2x+1} & \Rightarrow \quad y \ge 1-x \end{cases}

Therefore, the region is a right-angle triangle bounded by y = 2 y = 2 , x = 1 x=1 and y = 1 x y=1-x as shown in the figure below. The area is then 1 2 × 2 × 2 = 2 \dfrac{1}{2}\times 2 \times 2 = \boxed{2} .

Nice solution!!! Upvoted

Atul Shivam - 5 years, 2 months ago

Sorry but again exactly same solution!!

Aakash Khandelwal - 5 years, 2 months ago

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