Consider a region bounded by the x-axis and the line \( y = 2x \) from \( x = 0 \) to \( x = 1 \). If this shape is revolved around the x-axis, what is the volume of the resulting solid using triangular cross-sections perpendicular to the x-axis?
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To find the volume of the solid formed by revolving the region bounded by the x-axis and the line \( y = 2x \) from \( x = 0 \) to \( x = 1 \) around the x-axis, we can use the method of cylindrical shells or the disk method for integration. Given the line \( y = 2x \), we can express the height of the triangular cross-section at a given value of \( x \). The area of the triangular cross-section (with base on the x-axis and height along the line \( y = 2x \)) can be calculated as follows: 1. The triangle has a height \( h = 2x \). 2. The base of the triangle runs from \( x \) to 0 on the x-axis. 3. The area \( A \) of the triangle can be calculated as: \[ A = \frac{1}{2} \text{(base)} \times \text{(height)} = \frac{1}{2} (x - 0)(2x) = \frac{1}{2} \cdot 2x \cdot x = x^2. \] To find the volume of the solid, we will integrate the area of the triangular cross-sections from \( x = 0 \) to \( x = 1 \): \[ V = \int_{0}^{1} A \, dx = \int_{0}^{1} x^2 \, dx. \] Calculating the integral: \[ V = \int_{0}^{1} x^2 \, dx = \left[ \frac{x^3}{3} \right]_{0}^{1} = \frac{1^3}{3} - \frac{0^3}{3} = \frac{1}{3}. \] Thus, the volume of the resulting solid when the region is revolved around the x-axis is: \[ \boxed{\frac{1}{3}}. \]