Area of region bounded by inequalities

CAT 2020 Slot 1 · QA · Medium · Geometry

The area of the region satisfying the inequalities xy1|x| - y \le 1, y0y \ge 0, and y1y \le 1 is

(TITA)

Answer

3

Explanation

The given inequalities are:

  1. yx1y \ge |x| - 1
  2. y0y \ge 0
  3. y1y \le 1

Let's find the boundaries of the region in the xyxy-plane:

  • At y=0y = 0: x1    1x1|x| \le 1 \implies -1 \le x \le 1. Length of base =2= 2.
  • At y=1y = 1: x2    2x2|x| \le 2 \implies -2 \le x \le 2. Length of top side =4= 4.

The region bounded between y=0y = 0 and y=1y = 1 is a symmetric trapezoid with parallel sides a=2a = 2 and b=4b = 4, and height h=1h = 1.

Area=12×(a+b)×h=12×(2+4)×1=3\text{Area} = \frac{1}{2} \times (a + b) \times h = \frac{1}{2} \times (2 + 4) \times 1 = 3

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