If a line in 3 dimensions makes angles α, β, and γ with the positive directions of the coordinate axes, then what is cos(α + β)cos(α - β) equal to?

Find the equation of the line passing through the point (1, -2, 4) and parallel to the line x - 52 = y - 35 = z + 13.

For real numbers a, b, and c, find the coordinates of points in the YZ plane.

If the distance between the points (1, -1, 3) and (x, -4, 7) is 5, find the value of x.