On the error of approximation by ridge functions with two fixed directions

A. Kh. Asgarova, A. M-B. Babayev, I. K. Maharov

We consider the problem of approximation of a continuous multivariate function by sums of two ridge functions in the uniform norm. We obtain a formula for the approximation error in terms functionals generated by closed paths. 

Tbilisi Mathematical Journal, Vol. 10(2) (2017), pp. 111-120