Get the vector Norm without absolute values?

Question

I want to get the Norm of a vector which involves sines and cosines (So I really need to replace it by the Pythagorean theorem). Since I know that all my results are going to be real and positive I don't care about the Abs before squaring the terms.

How can I get $$ \sqrt{ r_x ^ 2 + r_y ^ 2 + r_z ^ 2 }$$

Instead of: $$ \sqrt{ |r_x| ^ 2 + |r_y| ^ 2 + |r_z| ^ 2 }$$

Sqrt[vec.vec] where vec is your vector. . in Mathematica is the dot product. — C. E., Apr 16 '17 at 19:34
@C.E. Thanks! I was doing it with loops but I didnt expect such elegant solution! Could you add it as an answer please? — Joshua Salazar, Apr 16 '17 at 19:41
As @BobHanlon says (and I thank you) ComplexExpand is more generalized solution to annoying complex numbers problem. — Chameleon, May 24 '20 at 16:10

score 8 · Accepted Answer · answered Apr 16 '17 at 20:01

8

That expression is the square root of the dot product of the vector by itself:

Sqrt[vec.vec]

where vec is your vector.

answered Apr 16 '17 at 20:01

C. E.

70,533
6
140
264

Get the vector Norm without absolute values?

1 Answers1

Linked