vectors-quick see.(II)

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20 Mar 2009 18:32:55 IST
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20 Mar 2009 18:32:55 IST
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vectors-quick see.(II)

Vector Product

DEFINITION : The vector product is fundamentally different from the scalar product. The vector product of two vectors is a vector but the scalar product is a scalar. The vector product is given by:

a

where
|a| = is the length of a or b
&theta = is the angle between vectors
n = is the unit vector perpendicular to a and b whose direction is determined by the left hand skew rule.
a

For vectors a x b is found by using the following:

a

For simplicity this can be written in terms of determinants

a
Now try the vector product yourself


DEFINITION :In terms of vectors the area of the triangle below is:
source=internet.

The Area of a Vector Triangle

 


a

Try finding the area of your own vector triangles


Recall that the vector equation of a plane is ( r - a ) . n = 0 where a is a point on the plane and n is a vector normal to the plane.
Say if we have points

components4

which are in Cartesian form. We firstly need to find the vector parallel to the plane.

a

To get a vector n, which is normal to the plane, we take the vector product of the above vectors.

a

This gives a vector denoted n by So the equation of the plane is found using the same method as above

By substituting in we get

a

Find the equation of your plane given three of your own points

DEFINITION : Skew lines are lines or vectors which are not parallel and do not meet. We now seek the minimum distance between these lines By drawing a line between both lines: called a transversal it will be perpendicular to both lines. a

The transversal connects A and B and n3 is the unit vector in the direction AB and p is the required distance.

As mentioned above n3 is perpendicular to both n1 and n2

a

Finding the Equation of a Plane given Three Points

 

Minimum distance between two skew lines

 

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