- 9

- 0

**a=3i+j-4k**

**b= 5i-3j-2k**

**c= 4i-j-3k**are

__COPLANAR__**2. Homework Equations**

__(axb)c=0__**3. The Attempt at a Solution**

If (axb)c=0 then c is orthogonal to axb and therefore c is in the plane perpendicular to axb since axb is perpendicular to both a and b, both a,b,c are in the same plane perpendicular to axb.

My problem is that my answer when using the formula doesnt equal 0 meaning that it isn't coplanar which means its wrong because i have to prove it is. Can someone show me a walkthrough and how to use this formula because im doing something wrong