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

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

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

__COPLANAR__## Homework Equations

__(axb)c=0__## 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