Question:medium

A man needs to hang two lanterns on a straight wire whose end points have coordinates A (4, 1, -2) and B (6, 2, -3). Find the coordinates of the points where he hangs the lanterns such that these points trisect the wire AB.

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Quick Tip: To trisect a line segment, use the section formula. The formula allows you to divide a line in a given ratio, which is useful when dividing a segment into equal parts.
Updated On: Jan 13, 2026
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Solution and Explanation

The wire connects points \( A(4, 1, -2) \) and \( B(6, 2, -3) \). Lanterns are positioned at points that divide the wire into three equal segments. These points, \( P_1 \) and \( P_2 \), trisect the line segment AB. \( P_1 \) is located closer to A, dividing the segment in a \( 1:2 \) ratio, while \( P_2 \) is closer to B, dividing the segment in a \( 2:1 \) ratio. The section formula is used to find these coordinates: \( x = \frac{m x_2 + n x_1}{m + n}, \quad y = \frac{m y_2 + n y_1}{m + n}, \quad z = \frac{m z_2 + n z_1}{m + n} \). 1. For \( P_1 \) (ratio \( 1:2 \), \( m=1, n=2 \)): \( x_1 = \frac{1 \cdot 6 + 2 \cdot 4}{1 + 2} = \frac{14}{3} \) \( y_1 = \frac{1 \cdot 2 + 2 \cdot 1}{1 + 2} = \frac{4}{3} \) \( z_1 = \frac{1 \cdot (-3) + 2 \cdot (-2)}{1 + 2} = \frac{-7}{3} \) Thus, \( P_1 \left( \frac{14}{3}, \frac{4}{3}, \frac{-7}{3} \right) \). 2. For \( P_2 \) (ratio \( 2:1 \), \( m=2, n=1 \)): \( x_2 = \frac{2 \cdot 6 + 1 \cdot 4}{2 + 1} = \frac{16}{3} \) \( y_2 = \frac{2 \cdot 2 + 1 \cdot 1}{2 + 1} = \frac{5}{3} \) \( z_2 = \frac{2 \cdot (-3) + 1 \cdot (-2)}{2 + 1} = \frac{-8}{3} \) Thus, \( P_2 \left( \frac{16}{3}, \frac{5}{3}, \frac{-8}{3} \right) \). The lantern positions are \( P_1 \left( \frac{14}{3}, \frac{4}{3}, \frac{-7}{3} \right) \) and \( P_2 \left( \frac{16}{3}, \frac{5}{3}, \frac{-8}{3} \right) \).
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