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
Anticrepuscular rays Anticrepuscular rays Anticrepuscular rays, or antisolar rays, are atmospheric optical phenomena similar to crepuscular rays, but appear opposite of the Sun in the sky. Anticrepuscular rays are nearly parallel, but appear to converge toward the antisolar point due to linear perspective. Anticrepuscular rays are most frequently visible around sunrise or sunset. Appearing to radiate from the Sun, crepuscular rays usually look much brighter than anticrepuscular rays. This is because the atmospheric light scattering making the crepuscular rays visible occurs at low angles to the horizon (see Mie theory). Although anticrepuscular rays appear to converge toward the antisolar point, the convergence