This constant is used in solutions of several extremal problems, for example • Favard's constant is the sharp constant in
Jackson's inequality for
trigonometric polynomials • the sharp constants in the
Landau–Kolmogorov inequality are expressed via Favard's constants • Norms of periodic
perfect splines. • The second Favard constant, K_2 = \frac{\pi^2}{8} is the same as the value of the internal 4-dimensional equivalent of the angles in a
tesseract. The first Favard constant is equal to the value of the internal solid angles in cubes, and the internal angles in squares. ==References==