1. The problem statement, all variables and given/known data State whether lines are || or perpendicular, and find the angle between the lines line A is given by the following parametric equations: x = 1 -3t y = 2 +4t z = -6 +t line B: x = 1 +2s y = 2 -2s z = -6 +s 2. Relevant equations 3. The attempt at a solution I looked at both z values -6+t = -6+s this is only true if and only if s = t for any value. Neverthless, I started with the dumb way, setting each equation equal to the other. 1 +2s = 1 -3t and we found s = -3/2 and substitute this back to the y equations. 2+4t = 2-2(-3/2) => t = 3/4 this clearly showed that s =/= t but and z cannot be equal... i looked at the book's answer, it gave me a cos-1 (-13/sqrt(234)) but only if lines are perpendicular there is an angle delta between the lines. neither skew nor || lines !!!! so why did the book answer the second question? there shouldn't even have an angle between the two planes.