Sonine formula

In mathematics, Sonine's formula is any of several formulas involving Bessel functions found by Nikolay Yakovlevich Sonin.

One such formula is the following integral formula involving a product of three Bessel functions:

${\displaystyle \int _{0}^{\infty }J_{z}(at)J_{z}(bt)J_{z}(ct)t^{1-z}\,dt={\frac {2^{z-1}\Delta (a,b,c)^{2z-1}}{\pi ^{1/2}\Gamma (z+{\tfrac {1}{2}})(abc)^{z}}}}$

where Δ is the area of a triangle with given sides.