Secants, tangents and differentiability

Thanks to Douglas N. Arnold who created this site, from which these images are taken.

Tangents from secants:
- secant approaches tangent
- tangent with tangent showing
- zoom-tangent: a smooth continuous function looks linear if you zoom in far enough
Slope discontinuities:
- infinite
- corner
Graphical issues for limits
Difference quotient demonstration:
Demonstration that

or
:
- difference quotient

Website maintained by Andy Long. Comments appreciated.