Working on truss, but outputs are a bit off.

format shortG

d = sind(45);

A=[-d 0 0 0 0 0 0 0 0 0; %ab

-d -1 0 0 0 0 0 0 0 0; %ac

0 0 0 0 -d 0 0 -1 0 0; %bc

0 0 0 0 -d 0 1 0 1 0; %bd

d 0 1 -d d 0 0 0 0 0; %be

d 0 0 -d -d 0 0 0 0 0; %dx

0 0 -1 0 0 0 0 0 0 0; % ce

0 1 0 0 0 0 -1 0 0 0; % de

0 0 0 d 0 1 0 1 0 0; %Rey

0 0 0 d 0 0 0 0 0 1;]; % Rdy

b=[1000;0;0;0;0;0;1000;0;0;0];

X = linsolve(A,b)

Someone please help me to get Fab = 1414.21; Fac = -1000; Fbc = 1000; Fbe = -707.107; Fbd = 2121.32; Fce = -1000; Fde = 500; Rdx = -2000; Rdy = -1500; Rey = 1500

Answer 1

[Steven Lord]

When I define a vector to contain your expected results and compute A*x-b, the residuals are quite large.

expected = [1414.21; -1000; 1000; 2121.32; -707.107; -2000; -1000; 500; 1500; -1500]
residuals = A*expected-b

residuals =
        -2000
     0.002519
   0.00015472
         1000
   -0.0024308
   -0.0021213
        -2000
            0
  -0.00024293
  -0.00024293

When I compute the residuals using the solution provided by linsolve they are quite small.

residualsLinsolve = A*X-b

residualsLinsolve =
            0
            0
            0
            0
   3.0996e-14
   8.2691e-14
   1.1369e-13
            0
            0
            0

If I use linsolve with -b instead of b, the solution matches your expected solution except for the next-to-last element, making me suspect 1) you made a typo in that next-to-last element and 2) you need to be careful about coordinate systems.

[Jaeyoung Lee]

-1414.2

1000

-1000

-2121.3

707.11

2000

1000

-500

-500

1500

This is what i get

[Steven Lord]

And what happens if you compute A*(that vector)-b? Are all the elements small?

[Jaeyoung Lee]

2.109

-1.4913

1.4913

3.1634

-1.0545

-2.9825

-1.4913

0.74563

0.74563

-2.2369

this is what i get

[Jaeyoung Lee]

So i am supposed to "Fac = -1000; Fbc = 1000; Fbe = -707.107; Fbd = 2121.32; Fce = -1000; Fde = 500; Rdx = -2000; Rdy = -1500; Rey = 1500 " for answers but i ended up having

-1414.2

1000

-1000

-2121.3

707.11

2000

1000

-500

-500

1500