Posted by Samantha on .
Let L1 be the line with the vector equation r= (2,3) +s(1,3), seR. Let L2 be with the line with parametric equation x=3t+2, y=t7, teR. Are L1 and L2 perpendicular? How do you know?

Calculus 
Reiny,
You have to look at their direction numbers
direction of L1 is (1,3)
for L2, the direction is (3,1)
since (3,1)⋅(1,3) = 0 , they are perpendicular.