What is the projection of <5,0,-2 ><5,0,2> onto <1,-1,0 ><1,1,0>?

1 Answer
Feb 14, 2016

vec c=<5/2,-5/2,0>c=<52,52,0>

Explanation:

vec a=<5,0,-2>a=<5,0,2>
vec b=<1,-1,0>b=<1,1,0>
vec a*vec b=5*1+0*(-1)+0*(-2)=5 ab=51+0(1)+0(2)=5
"dot product between vec a and vec b;"dot product between vec a and vec b;
|b|=sqrt(1^2+1^2+0^2)=sqrt 2|b|=12+12+02=2
vec c=(vec a*vec b)/(|b|*|b|)*vec bc=ab|b||b|b
vec c=5/(sqrt 2*sqrt 2)*<1,-1,0>c=522<1,1,0>
vec c=5/2<1,-1,0>c=52<1,1,0>
vec c=<5/2,-5/2,0>c=<52,52,0>