eng Science and Education Publishing American Journal of Mathematical Analysis 2013-11-03 1 1 42 47 10.12691/ajma-1-3-4 AJMA2013134 article Binod Prasad Dhakal binod_dhakal2004@yahoo.com 1 Tribhuvan University, Nepal The Jacobi polynomial P_n⁽α^,β⁾(x) which is obtained from Jacobi differential equation is an orthogonal polynomial over the interval [-1, 1] with respect to weight function _(1-x)α_(1+x)β, α>-1, β>-1. Here Jacobi series has been taken and established a theorem on lower triangular matrix summability of a Jacobi series. http://pubs.sciepub.com/ajma/1/3/4/ajma-1-3-4.pdf summability jacobi series triangular matrix