--                                                  --     --  --
|.7071  0    0    -1   -.8660     0    0    0    0   |     | 0  |
|.7071  0    1     0     .5       0    0    0    0   |     |1000|
|  0    1    0     0      0      -1    0    0    0   |     | 0  |
|  0    0   -1     0      0       0    0    0    0   |     | 0  |
|  0    0    0     1      0       0    0    0  -.7071| F = | 0  |
|  0    0    0     0      0       0    1    0   .7071|     |-500|
|  0    0    0     0    .8660     1    0   -1    0   |     | 0  |
|  0    0    0     0    -.5       0   -1    0    0   |     | 500|
|  0    0    0     0      0       0    0    1   .7071|     | 0  |
--                                                  --     --  --

How this linear system of equations was derived:
------------------------------------------------
In a statically determinate trust with frictionless pin joints,
the tension (Fi) in each member can be obtained from setting the
sums of all forces acting horizontally or vertically at each pin
equal to zero, the angle at each of the junction is indicated
above):

down | negative (-)    left <- negative (-)    is convention
    \-/

joint1 is fixed

joint2: x    sin pi/4 F1 - F4 - sin pi/3 F5        = 0  [row1]
        y    cos pi/4 F1 + F3 + cos pi/3 F5 - 1000 = 0  [row2 after
                                                        move -1000]

joint3: x                                  F2 - F6 = 0  [row3]
        y                                      -F3 = 0  [row4]

joint4: x                         F4 - cos pi/4 F9 = 0  [row5]
        y                   500 + F7 + sin pi/4 F9 = 0  [row6 after
                                                        move 500]

joint5: x                   -F8 + F6 + sin pi/3 F5 = 0  [row7]
        y                  -500 - F7 - cos pi/3 F5 = 0  [row8 after
                                                        move -500]

joint6: x                         F8 + cos pi/4 F9 = 0  [row9]
        y    n/a  (since on rollers and no vertical motion)

cos(pi/4)=sin(pi/4)=.7071
sin(pi/6)=cos(pi/3)=.5