I need to evaluate if two lines are perpendicular and give a reason for my answer.
So: To show that the lines are not perpendicular, I need to show by the dot product method that my calculation does not = 0. Because cos(0)=90, perpendicular lines.
I have two lines below:
I need to start with my components in (i, j, k) form.
The angle between the lines is the angle between their directions. The directions are U and V.
u.v=(2, 4, -3)(1, 5, 1)=(2+20-3)=19
Is this enough or do I need to go further, i.e
θ=but when I inverse cos I get a mathematical error when I try to inverse cos this figure?