Concave function Concave function In mathematics, a concave function is the negative of a convex function. A concave function is also synonymously called concave downwards, concave down, convex upwards, convex cap or upper convex. A real-valued function formula_1 on an interval (or, more generally, a convex set in vector space) is said to be "concave" if, for any formula_2 and formula_3 in the interval and for any formula_4, A function is called "strictly concave" if for any formula_7 and formula_8. For a function formula_9, this second definition merely states that for every formula_10 strictly between formula_2 and formula_3, the point formula_13 on
Parallel projection central or perspective projection, in which the rays pass through a fixed point called the "center" or "viewpoint", as this point is moved towards infinity. Put differently, a parallel projection corresponds to a perspective projection with an infinite focal length (the distance between the lens and the focal point in photography) or "zoom". In parallel projections, lines that are parallel in three-dimensional space remain parallel in the two-dimensional projected image. A perspective projection of an object is often considered more realistic than a parallel projection, since it more closely resembles human vision and photography. However, parallel projections are popular in