Posted by **jenna** on Thursday, May 17, 2012 at 4:56pm.

given v=5i+3j and w=-4i+8j, find projwv

- trigonometry -
**Damon**, Thursday, May 17, 2012 at 5:08pm
There are two kinds of projection of w on to v or of v on to w.

You did not say projection of which on the other or if you want scalar or vector projection.

see below:

Projections

One important use of dot products is in projections. The scalar projection of b onto a is the length of the segment AB shown in the figure below. The vector projection of b onto a is the vector with this length that begins at the point A points in the same direction (or opposite direction if the scalar projection is negative) as a.

Thus, mathematically, the scalar projection of b onto a is |b|cos(theta) (where theta is the angle between a and b) which from (*) is given by

This quantity is also called the component of b in the a direction (hence the notation comp). And, the vector projection is merely the unit vector a/|a| times the scalar projection of b onto a:

Thus, the scalar projection of b onto a is the magnitude of the vector projection of b onto a.

- trigonometry -
**Damon**, Thursday, May 17, 2012 at 5:11pm
Here:

http://www.math.oregonstate.edu/home/programs/undergrad/CalculusQuestStudyGuides/vcalc/dotprod/dotprod.html

- trigonometry -
**ky**, Thursday, May 17, 2012 at 5:21pm
it was proj with w as a subscript of proj and then v

- trigonometry -
**Damon**, Thursday, May 17, 2012 at 5:27pm
I am sorry. I am not familiar with that notation. Follow the recipe in the link I gave you.

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