Let σ1, σ2 be two planes; n1, n2 be the unit normals to the planes σ1, σ2 respectively.
Then (n1, n2), 180° – (n1, n2) are called the angles between two planes σ1 and σ2.
If n1 and n2 are unit normals to the planes
r.n1 = d1 and r .n2 = d2 and θ is the angle between the normals, then
cos θ =
If the two planes are perpendicular to each other, then n1.n2 = 0
If the two planes are parallel, then n1 is parallel to n2.
(i) The component of b on a =
(ii) The component of a on b =
(iii) The orthogonal projection of b on a =
(iv) The orthogonal projection of a on b =