TI-84 Tips to Show Curves are Orthogonal To Each Other (2.5 #63)

 TI-84 Tips to Show Curves are Orthogonal To Each Other (2.5 #63)

Here we use a TI-84 to show how two curves are orthogonal to each other.  If they are, then the tangent lines's slope at the points of intersection are perpendicular, and be negative reciprocals of each other:

If the slope is a/b, then the perpendicular slope is -b/a.  The calculator has a (CALC)5. intersect feature and a (CALC)6. dy/dx feature, so this is how we can tell if the curves are orthogonal.