So I have a Structures Analysis II test tomorrow.... and some of the things that are gonna be on it are from Analysis I, and to find the displacement of uniaxial elements, beams, trusses, and frames Ive always implemented the function into my calculator the same way every time.... and the night before the test my calculator is spitting out an error message cause im trying to take the inverse of a matrix whos determinant is 0! But its worked every time before.... heres the email i sent my teacher, if any of you guys know anything about graphic calculators, Ti-84 Plus in particular, please let me know, ill be up at 6:30am and have time to figure this out by 11:00am.... thanks

I was trying to figure out the d's for a uniaxial element that I had
worked out by hand. I have occured a problem within my calculator that I
have never seen before, and this method has worked every time. I entered
my Q into my calculator as a 2x1, Qf as a 2x1, and my k as a 2x2.... the k
is going to be a number (EA/L) * [1 -1; -1 1] so I put that into the
matrix as [EA/L -EA/L; -EA/L EA/L].... to solve this equation to get the
d's, since 325 I have inputed it as [k]inverse*([Q]-[Qf]) and the
calculator is giving me an error message saying Singular MAT which is
singular matrix. I know that the determinant of a #*[1 -1; -1 1] is zero
and that you cant take the inverse of 0 but my calculator has never gotten
stumped on that. Ive tried reseting my calculator and that didn't work.
I asked one of the Mielke's to do the inverse of [1 -1; -1 1] in his
calculator and it worked fine. Do you have any solution to my problem. I
just dont wanna have to solve something like that on the test and spend
the time dividing out matrices. Thanks.

 

My ***** itch. Also I loaned out my calc and never got it back.[>:]

 

Ohhh! Have you tried entering the sqaure root of a negative reality inversion into it yet? I find that usually helps.

 

I figured out my problem right after I posted this, i guess it was just good for me to write out my problem, for any of you who know structural analysis, you cant solve the the displacements using just the {Q}, {Qf} and [k] matrices, its late, and i had a glitch in the brain.... i forgot to use the code number method on the {Q}={Qf}+[K]{u} to get the {P}={Pf}+[S]{d} <== and thats where you get the d's from

 

Try graphing the point. Using it in a equation will not allow undefined values, but graphing it will allow those values to come back.

It may work, it may not. I used to have that problem with some problems, and instead of just imputing it as a problem, try graphing it.

 

D2DGraphix_600RR, you cant graph a matrix.... unless your talkin about doing each one separat such as Qij=Qfij+kij*u

 

You can but you have to do is separate and work backwords

 

But you figured it out...

 

yea separate and work backwards is what i was talking about with the ij's

D2D, i understand what your saying, thanks tho mang!

 

I just started college ....and im already struggling with business calculus lol i ****in hate math [:@]