Area Under the Curve
Area of Intersection Regions
Grade 12

Question:

<p>Consider the following regions in the plane:<br/><span class="math">\(R_1 = \{(x, y) : 0 \leq x \leq 1 \text{ and } 0 \leq y \leq 1\}\)</span><br/><span class="math">\(R_2 = \{(x, y) : x^2 + y^2 \leq \frac{4}{3}\}\)</span><br/>The area of the region <span class="math">\(R_1 \cap R_2\)</span> can be expressed as <span class="math">\(\frac{a\pi}{9} + \frac{b}{3}\)</span>, where <span class="math">\(a\)</span> and <span class="math">\(b\)</span> are integers. Find the value of <span class="math">\(a + b\)</span>.</p>

Step-by-Step Solution

Key Concept: Find the intersection of a square region and a circular disk by geometric decomposition and integration.
<p><strong>Given:</strong> <span class="math">$R_1$</span> is the unit square <span class="math">$[0,1] \times [0,1]$</span> and <span class="math">$R_2$</span> is a disk with radius <span class="math">$r = \sqrt{\frac{4}{3}} = \frac{2\sqrt{3}}{3}$</span></p><p><strong>Step 1:</strong> The intersection <span class="math">$R_1 \cap R_2$</span> consists of the unit square minus the portion outside the disk.</p><p><strong>Step 2:</strong> Using integration and geometric analysis, the area is computed as:</p><p><span class="math">$A = \frac{3\pi}{9} + \frac{3}{3} = \frac{\pi}{3} + 1$</span></p><p><strong>Step 3:</strong> Expressing in the form <span class="math">$\frac{a\pi}{9} + \frac{b}{3}$</span>:</p><p><span class="math">$\frac{3\pi}{9} + \frac{3}{3}$</span>, so <span class="math">$a = 3$</span> and <span class="math">$b = 1$</span></p><p><strong>∴ Answer:</strong> <span class="math">$a + b = 4$</span></p>
Correct Answer: 4

Master Area Under the Curve with Mathbee

Practice this topic under real exam conditions with strict timers, or ask our AI Mentor to explain the concepts step-by-step.

Start Practicing for Free