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## Archive of Issues

Russia Izhevsk
Year
2012
Issue
1
Pages
144-154
 Section Computer science Title Exact formulas for coefficients and residual of optimal approximate spline of simplest wave equation Author(-s) Rodionova N.V.a Affiliations Udmurt State Universitya Abstract We define the parameter family of finite-dimensional spaces of special quadratic splines of Lagrange's type. In each space, the optimal spline which gives the smallest residual being a square of the norm in the space $L_2$, is proposed as a solution to the initial-boundary problem for the simplest wave equation. The exact formulas for the coefficients of the spline and its residual are obtained. The formula for the coefficients of this spline is a linear form of finite differences of the discretely given initial and boundary conditions of the original problem. The formula for the residual $J$ is a positive definite quadratic form of these quantities. The coefficients of both forms are computable via Chebyshev's polynomials of the second kind. The explicit form of the formula for the residual allows to solve the inequality $J<\varepsilon^2$ for a given computing accuracy $\varepsilon>0$ and to receive a priori sufficient number of nodes of a difference scheme. The investigations were carried out for one time layer, which has two sublayers. We obtained difference formulas of the initial condition for the partial derivative with respect to time. They allow to create a difference scheme for the new layer, which in turn allows to continue the iterative computational process in time as far as desired. Keywords interpolation, approximate spline, residual, Chebyshev’s polynomials UDC 519.651, 517.518.823 MSC 41A15 DOI 10.20537/vm120112 Received 11 October 2011 Language Russian Citation Rodionova N.V. Exact formulas for coefficients and residual of optimal approximate spline of simplest wave equation, Vestnik Udmurtskogo Universiteta. Matematika. Mekhanika. Komp'yuternye Nauki, 2012, issue 1, pp. 144-154. References Rodionov V.I. On application of special multivariate splines of any degree in the numerical analysis, Vestn. Udmurt. Univ. Mat. Mekh. Komp. Nauki, 2010, no. 4, pp. 146–153. Rodionov V.I., Rodionova N.V. Exact formulas for coefficients and residual of optimal approximate spline of simplest heat conduction equation, Vestn. Udmurt. Univ. Mat. Mekh. Komp. Nauki, 2010, no. 4, pp. 154–171. Suetin P.K. Klassicheskie ortogonal’nye mnogochleny (Classical orthogonal polynomials), Moscow: Nauka, 1976, 328 p. Full text