# Thread: Lesson 8-4 Perpendicular Vectors: Cross products

1. ## Lesson 8-4 Perpendicular Vectors: Cross products

Use the definition of cross products to prove that for any vectors, a, b, c,
a x (b + c) = (a x b) + (a x c)
*the variables have a little arrow on top of them
please show all work for this problem

2. ## Re: Lesson 8-4 Perpendicular Vectors: Cross products

Originally Posted by Vileblood
Use the definition of cross products to prove that for any vectors, a, b, c, a x (b + c) = (a x b) + (a x c)
please show all work for this problem
Why have you not shown any work whatsoever?

3. ## Re: Lesson 8-4 Perpendicular Vectors: Cross products

I don't know where to begin with this problem.

4. ## Re: Lesson 8-4 Perpendicular Vectors: Cross products

Originally Posted by Vileblood
I don't know where to begin with this problem.
Since the instructions say to use the definition of a cross product, I'd start there.

5. ## Re: Lesson 8-4 Perpendicular Vectors: Cross products

Originally Posted by Vileblood
I don't know where to begin with this problem.
Start with $\displaystyle a=<a_x,a_y,a_z>,~b=<b_x,b_y,b_z>,~\&~c=<c_x,c_y,c_ z>$.

Then use the definitions to find $\displaystyle a\times b + a\times c$.

Then try to unpack it to get $\displaystyle a\times(b+c)$.