5 resources.
Direction cosines and direction ratios: converting between them, the identity l² + m² + n² = 1, worked examples from axes, two points, angles and the angle between lines, and common mistakes.
The equation of a line in 3D in vector and Cartesian form: through two points or a point and a direction, checking whether a point lies on a line, the angle between two lines, and common mistakes.
Every standard form of a plane's equation, finding a plane from a point and normal or three points, intercept form, planes through an intersection, and point-to-plane distance.
The angle between a line and a plane, two lines, and two planes, plus the parallel and perpendicular tests, with worked examples and common mistakes.
The shortest distance between skew lines and between parallel lines in vector form, how to tell intersecting lines apart, the Cartesian determinant form, and three worked examples.