Practice Lines in 3D in Math

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

Lines in three-dimensional space described using parametric equations x = x_0 + at, y = y_0 + bt, z = z_0 + ct, or symmetric form \frac{x - x_0}{a} = \frac{y - y_0}{b} = \frac{z - z_0}{c}, where (x_0, y_0, z_0) is a point on the line and \langle a, b, c \rangle is the direction vector.

In 2D, a line is defined by a slope and a point (y = mx + b). In 3D, slope doesn't workβ€”there's no single number for direction in space. Instead, you specify a starting point and a direction vector (an arrow pointing along the line). The parameter t acts like a slider: at t = 0 you're at the starting point, and as t increases or decreases, you slide along the line in the direction of the vector.

Example 1

easy
Write parametric equations for the line through the point (2, -1, 3) in the direction of the vector \langle 4, 1, -2 \rangle.

Example 2

medium
Find parametric equations for the line through (1, 0, -2) and (3, 4, 1).

Example 3

medium
Determine whether the lines \ell_1: x = 1+t, y = 2-t, z = 3+2t and \ell_2: x = 3+2s, y = -s, z = 7+4s are parallel, intersecting, or skew.

Example 4

hard
Find the distance between the parallel lines \ell_1: \frac{x-1}{2} = \frac{y}{1} = \frac{z+1}{-1} and \ell_2: \frac{x-3}{2} = \frac{y-1}{1} = \frac{z}{-1}.