HINT:
use the property that v1.v2=0 , if v1,v2 are perpendicular.

OK.so, let A(2,-6,1); B(3,4,-2); C(7,-1,5) be given.
Now lets  find BC vector, which comes BC(4,-5,7).
Now suppose a point P(x,y,z) in between B and C.and draw perpendicular from A to this point P .
We can find AP vector which is AP(x-2,4+6,z-1).
now dot product of AP and BC is zero. From here you get P.Once you have P. The |AP| is the required distance

How to find the distance using dot product from point $A$ to the line through $B$ and $C$?
I mean when the cursor is on the left side of the words ,I would like to remove the words on the immediate right side of it . CTR+k remove everything on the right side, i only want one word to be removed. 
