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Mathematics 9 Online
OpenStudy (anonymous):

Good afternoon! Can someone explain the Vectors in the plane.

OpenStudy (anonymous):

vectors in one plane... that would mean in two dimensions? Just go through the first section here. http://www.physicsclassroom.com/class/vectors/

OpenStudy (anonymous):

There's two basic operation for vectors right? The scalar multiplication and vector addition. What is the difference between of two of them?

OpenStudy (anonymous):

oh, I thought you were looking for general information on vectors. You want to know the difference between the scalar or dot product and the vector or cross product?

OpenStudy (anonymous):

Yes all about the vectors.

OpenStudy (anonymous):

all about vectors is too much to teach in one day, but I could try to find websites for you to learn from. what math class are you in so I can know what exactly you want me to teach?

OpenStudy (anonymous):

No. I just need to have someone who is willing to share some ideas about vectors then I will share what I've know in vectors. If its alright to you?

OpenStudy (anonymous):

ok. vectors represent moving from one point to another. They have a magnitude and direction, but are usually represented by an x-coordinate and a y-coordinate in 2 dimensions.

OpenStudy (anonymous):

vectors add by placing the vectors tip-to-tail and seeing where it goes or by breaking down the vectors into their x and y components and adding all the components.

OpenStudy (anonymous):

the dot product or scalar product is the vector operation where you multiply one vector A by the component of another vector B that is parallel to it. The product is a scalar. It is given by AB sin (the angle between the two vectors)

OpenStudy (anonymous):

the scalar product of two vectors A and B with the components \[(X _{a}, Y_{a}) and (X_{b}, Y_{b})\] is \[X_{a} \times X_{b} + Y_{a} \times Y_{b}\]

OpenStudy (anonymous):

the cross product or vector product of two vectors is the vector operation where you multiply one vector A with the component of vector B that is perpendicular to vector A. The resultant vector is perpendicular to both vector A and vector B, in the direction given by the right hand rule. (ask your math teacher, I dont think I can explain this one here.)

OpenStudy (anonymous):

For example, I am asked to show that if A is any vector and c is any scalar 0(A)=0 and c(0)=0. How will I compute the magnitude of vector cA?

OpenStudy (anonymous):

the magnitude of cA will be c times the magnitude of vector A. do you need to know how to find the magnitude of a vector?

OpenStudy (anonymous):

Yes. I just remember the difference of two vectors. If the difference of vectors A and B, it is denoted by A-B, is the vector obtained by adding A to the negative of B or rather A-B = A+(-B). Am I right?

OpenStudy (anonymous):

Yes, you are right.

OpenStudy (anonymous):

In orthogonal vectors, two vectors A and B are said to be orthogonal or perpendicular if and only if A DOT B = 0.

OpenStudy (anonymous):

yes, by definition of the dot product, if two vectors are perpendicular their dot product is zero.

OpenStudy (anonymous):

\[A\cdot B = |A||B|\cos\theta\] If orthogonal implies\[\cos\frac{\pi}{2}=0\] Hence\[A\cdot B =0\]

OpenStudy (anonymous):

Just saying, the identity\[A\cdot B = |A||B|\cos\theta\] is not the definition of dot product. If I recall, this can be traced back to the Cauchy-Schwarz theorem where\[(A\cdot B)^2 \leq |A|^2|B|^2\] Equality holds when \[A=B\]

OpenStudy (anonymous):

Or you can use the law of cosine if you like.

OpenStudy (anonymous):

Most of the time we use the law of cosine in our discussion.

OpenStudy (anonymous):

It is indeed more straightforward.

OpenStudy (anonymous):

A sneak peek in cross product. A cross product between 2 vectors produce the third vector which is orthogonal to both the original 2 vectors.

OpenStudy (anonymous):

Is that a theorem?

OpenStudy (anonymous):

It is the definition

OpenStudy (anonymous):

ok.Thanks

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