Porisma

A hint to get started

Use normals for parallel planes and lines inside a plane

(a) Plane Π passes through A=(2,0,0) parallel to −2i+j+k-2\mathbf i+\mathbf j+\mathbf k and i−3j+2k\mathbf i-3\mathbf j+2\mathbf k.

(i) Find Π in scalar-product form and verify B=(6,−5,1) lies on it. marks

(ii) Find the position vector of the perpendicular foot from C=(−2,1,−3) to Π. marks Hence find the equation of a parallel plane Π1 such that C is equidistant from Π and Π1. marks

(b) Line l and plane P are l:r=λ(u+v)l:\mathbf r=\lambda(\mathbf u+\mathbf v), λ real, and P:r⋅(u×v)=0P:\mathbf r\cdot(\mathbf u\times\mathbf v)=0, with u,v nonzero and nonparallel.

(i) Show l is contained in P. marks

(ii) For u=(−1,2,1), v=(3,−3,2), find a line in P perpendicular to l through the origin. marks

[2008/MJC/Promo/11]

CJC · Review problems · Question 6

Containment requires a point as well as an appropriate direction.

Read the worked solution