# Multiplying Vectors

1. Sep 11, 2007

### jbp890

1. Show that the area of the triangle contained between vector a and vector b and the red line is 1/2 |a x b|

So far i have that bcosO would equal a ...and that 1/2bh should be the area... but im stuck. can somebody help me prove?

Last edited: Sep 11, 2007
2. Sep 11, 2007

### D H

Staff Emeritus
$b\cos\theta=a$ is not correct. Assuming vector b forms the base of the triangle, $A=1/2bh$ is the correct equation for the area. So what is the height of the triangle? (Hint: it involves only a and theta).