There are two vectors (d and c). d dot c will equal 50. The angle between them is 60 degrees (when the two vectors are tail to tail). What is ID X CI ?

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- Jun 11th 2012, 04:32 PMClairvoyantskiVectors
There are two vectors (d and c). d dot c will equal 50. The angle between them is 60 degrees (when the two vectors are tail to tail). What is ID X CI ?

- Jun 11th 2012, 06:52 PMHallsofIvyRe: Vectors
In order to do this equation, you need to know that d dot c= |d||c|cos(theta) where theta is the angle between them. I started to write "to find ID X CI" you would have to know what 'ID' and 'CI' mean" when it hit me that you

**mean**|D X C|, the**length**of DXC. Of course, to do that you have to know that that length is given by |D||C| sin(theta). - Jun 11th 2012, 08:51 PMSorobanRe: Vectors
Hello, Clairvoyantski!

I have a rather roundabout solution . . .

Quote:

Code:`C * - - - - - * B`

/ \ /

/ \ /

c / \ /

/ \ /

/ 60d \ /

A * - - - - - * D

d

. . where

We know that is the**area**of the parallelogram.

Formula: .

So we have: .

The area of is given by: .

The area of parallelogram is: .

Therefore: .