I made a mistake with the wording.

We know so far that A.C = 0 and B.C = 0. Therefore, to prove the above statement....

C.(mA + nB) = C.mA + C.nB

Using scalar properties, C.mA + C.nB = m*(A.C) + n*(B.C)

m*(A.C) + n*(B.C) = m*0 + n*0 = 0

Is it really that easy?

]]>And I think we do a great job helping people, keeping spammers out, and generally making this a really nice place.

The way we have reacted so strongly here is an indication of our good nature.

If we want to discuss this more, how about over in "Dark Discussions" ... ?

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Forum Rules:No Personal Attacks or Put-Downs. This is a type of bullying, and just makes you look insecure.

This is not a place to be mean to others and these posts will not be tolerated. Light banter or constructive criticism can be allowed if it is polite and friendly. Remember, other people have feelings too. "Those who give respect shall receive it."

It's alright to deviate though. That's just a natural part of conversation, señor.

]]>Senor, correct me if I am wrong.

mathsyperson wrote:

(And it is senior.)

That was intentional.

Abbr. Sr.

Used as a courtesy title before the surname, full name, or professional title of a man in a Spanish-speaking area.

Used as a form of polite address for a man in a Spanish-speaking area.

(Spanish)

Anyway, haven't you pretty much got it already?

a.b = |a||b| cos θ, and if the dot product is 0, then the vector is perpendicular.

Take the angle between A and C to give A.C = |A||C| cos 90, which is 0, as you've said.

Multiplying A by m just gives Am.C = |Am||C| cos 90, which is still 0, so they are still perpendicular.

The same reasoning could be applied with B and C.

]]>Insomnia, the new moderator : Please note.

Mathsyperson, my senior in this forum : Senor, correct me if I am wrong.]]>

I was asking a question - I didn't expect to be ridiculed (i.e. Insomnia and Person). Nice to see that internet etiquette is at its best in this forum.

Thank you for your reply, MathsIsFun. As for the other two, keep your bragging for the locker room.

]]>A scalar does not change direction of a vector.

(Different of course if a vector is the resultant of two other vectors, and those vectors change length)

]]>My Thoughts....

If we have perpendicular vectors on a 2D plane, then V.W = 0 when the dot product of vectors V and W is found.

It can also be seen from the dot product formula that V.W = ( V ) ( W) cos 90 and cos 90 = 0.

But how to prove they are perpendicular after being multiplied by scalars remains the question.

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