Recent content by JosephR

If You have an Matrix nxn ~> It's dimension= nxn for example the dimension of a 3x5 matrix is 15 if you have a polynimial it's dimension is n+1 And if You have for Example R^n it's dimension is n.

THANK YOU DUDE ! u really helped me :)

you mean i should assume that A is invertible and prove that AAT is invertible also ...

Homework Statement A martix A is said to idempotent if A²=A prove the following: a) If A is idempotent then I-A is also idempotent b) If A is idempotent and invertible then A=I c) If A is idempotent then I-2A is invertible.Find (I-2A)-1 in terms of A d)Give an example of a 2x2 idempotent...

i haven't taken determinant till now.. is there any other way to do it ?

Homework Statement Show that if AAt(where At is the transpose of A) has no inverse,Then A itself cannot have an inverse 2. The attempt at a solution Here's what i did AAt.(AAt)-1=AAt.At-1A-1=AA-1=I thus AAt has an inverse IF and only IF A is invertible and since AAT has no...

hey tiny-tim:) i knew this but it would take some time to be solved ! because sin²(x/3)=[1-cos(2x/3)]/2 anyway thanks buddy !

Homework Statement Find The length of r=sin³(x/3) 0<x<3pi/2 2. The attempt at a solution well first i found r'=3.cos(x/3).1/3.sin²(x/3)=cos(x/3)sin²(x/3) r²=cos²(x/3)sin^4(x/3) then i put the formula integral of radical (r'²+r²)dx and I'm stuck here any help?

Hello guyz,i'm facing this problem in my statics class...and thought posting it here so i can get some help :) here it goes http://img372.imageshack.us/img372/6241/58856343aw8.jpg Ok this is what i did and I'm kinda stuck... just bare with me...

Civil engineering ! Hello,I'm a student that is studying civil engineering and i can't see any subforum concerning civil engineering ! why is that ?:) Thanks ...and sorry if i posted this in the wrong section