How do I multiply a vector by a scalar like 4?

[DB]

when a question gives u vectors in polar form, calling them A,B,C,D then askes you to simply for example: A - 4C + D, what am i supposed to do? is it just vector sum and difference? how do i multiply a vector by 4?

thanks

 

[mathmike]

4(xi+yj+zk)=4xi+4yj+4zk

 

[DB]

sry i didnt mention we were working in 2D, but wat are i and j?

 

[mathmike]

i and j is the subscript used to designate the x and y axis

 

[DB]

o i see, sry to be a pain in the butt, but then wat are x and y?

 

[mathmike]

the coefficients of i and j

 

[Integral]

As used above, i and j, represent unit vectors, i in the x direction, j in the y. In 3d you also have k, the unit vector in the z direction.

I would assume that you are taking some form of a math class, have you read your text?

 

[DB]

so 4 * Vector 25, 340 degrees would be 4(23.5+8.6) aproxx??

 

[DB]

As used above, i and j, represent unit vectors, i in the x direction, j in the y. In 3d you also have k, the unit vector in the z direction.
I would assume that you are taking some form of a math class, have you read your text?

physics, my teacher hasnt given us any reading, he just said see if u can get these problems

 

[DB]

is 4(23.5+8.6) right? wat i did was set up the the vector on a cartesian plane and use trig to solve the lenghts, would it be 4(23.5+ -8.6) because the triangle is in the 4th quadrant, or would i take the absolute value?

 

[finchie_88]

If you are trying to work out 4V as a vector, and V is something at 340 degrees, and at a magnitude of 25, then the vector can be written as
$$v = 4(23.5i-8.6j)$$
(approx). The i and j are there to show they are the different components of v.
By the way, I hate this latex thing, I was trying to get the i and j go bold in tex mode, but failed, oh well.