Bounds for Orthogonal Expansion Coefficients via Weighted Primitives

For trigonometric and polynomial orthogonal expansions, we present coefficient bounds with anexplicit numerator determined by the total variation of the function and the largest cumulativesigned area of the weighted basis element. This area, denoted by 𝑀𝑛, is the sharp constant in thecorresponding weighted integral estimate. We calculate or bound 𝑀𝑛 for several classical systems,thereby obtaining quantitative inequalities beyond an asymptotic statement of coefficient decay.Integration between consecutive zeros gives a geometric interpretation of the estimate. The comparisonincludes Chebyshev polynomials of the first three kinds, Legendre, Jacobi, Gegenbauer,and ordinary Laguerre polynomials, with normalization and boundary conditions stated explicitly.Classical estimates and their elementary consequences are organized as Fourier analysis in inequalities.In the controlled-distortion application, ideal curves have selected coefficients absent, andrestrictions on the variation, corridor width, and number of extrema of admissible departures giveexplicit guarantees for those coefficients.