Concave function pointwise minimum of two concave functions, i.e. the set of concave functions on a given domain form a semifield. 3. Near a local maximum in the interior of the domain of a function, the function must be concave; as a partial converse, if the derivative of a strictly concave function is zero at some point, then that point is a local maximum. 4. Any local maximum of a concave function is also a global maximum. A "strictly" concave function will have at most one global maximum. Concave function In mathematics, a concave function is the negative of a convex function.
Lens (optics) real object at the location of that virtual image. Likewise, it appears to a subsequent lens as if it were an object at that location, so that second lens could again focus that light into a real image, "S" then being measured from the virtual image location behind the first lens to the second lens. This is exactly what the eye does when looking through a magnifying glass. The magnifying glass creates a (magnified) virtual image behind the magnifying glass, but those rays are then re-imaged by the lens of the eye to create a "real image" on the retina.