Question

Find the image of :
(i) (-2,3,4) in the yz- plane.
(ii) (5,2,-7) in the xy-plane.

Answer 1

Image of point wrt plane

If a coordinae of a point is represented by $(a,b,c)$ then its image in

$xy$ (say) is given by $(a,b,-c)$

Image of $(a,b,c)$ in xy-plane $\Rightarrow$ $(a,b,-c),,,,\left(1\right)$

Image of $(a,b,c)$ in yz-plane $\Rightarrow$ $(-a,b,c)....\left(2\right)$

Image of $(a,b,c)$ in zx-plane $\Rightarrow$ $(a,-b,c)....\left(3\right)$

(i) Fading image of $(-2,3,4)$ in yz plane is given by image of $(-2,3,4)$ in yz plane is $(2,3,4)$

(from (2))

(ii) finding image of $(5,2,-7)$ in xy plane is given by image of $(5,2,-7)$ in xy plane is $(5,2,7)$

(from (1))