# Calculate turning points

This graph e.g. has a maximum turning point at (0|-3) while the function has higher values e.g. in (2|5). This implies that a maximum turning point is not the highest value of the function, but just locally the highest, i.e. there is no higher value at least in a small area around that point.

So the basic idea of finding turning points is:

- Find a way to calculate slopes of tangents (possible by differentiation).
- Find when the tangent slope is . There could be a turning point (but there is not necessarily one!)

This means: To find turning points, look for roots of the derivation.

or a mininum turning point

or the slope just becomes for a moment though you have no turning point. Such a point is called saddle point.