strong_prob3.m

drlt 边界限元程序

%% Integrate f(x) = 6x/(2x^2+x-1) on [-2 2]

eta_strong=[-0.03969687 0.33333333 0.83969687];
weights_strong = [ -2.05166852 1.58823529 0.46343322];

%%% split in f(x) = 1/(x-0.5) + 2/(x+1)

%% integrate 1/(x-0.5) on [-2,2]

int_1_1=-1 * [1 1 1] * weights_strong' - log(2.5)

int_1_2=     [ 1 1 1] * weights_strong' + log(1.5)

%% integrate 2/(x+1) on [-2,2]

int_2_1= -2 * [1 1 1] * weights_strong' - 2*log(1)

int_2_2=  2 * [1 1 1] * weights_strong' + 2*log(3)


int = int_1_1 + int_1_2 + int_2_1 + int_2_2

%direct analytically
intan=3*log(3)-log(5)

x=(-2:0.01:2);
y=6*x./(2*x.*x+x-1);
figure(3)
plot(x,y,'Linewidth',2)
title([' Problem 3: f(x)'],'Fontsize',16)
grid on;