# Kirchhoff's Law

1. Mar 21, 2004

### nightwing

This is more of a calculator problem, we are currently doing Kirchhoff's Law in class and we are using the equation [A]^-1 x [X], where A is a 3x3 matrix containing the I3=I1+I2 and the V Rise and V Drop equations and the X is a matrix of the voltage values.
Ex.(I1)=(I2)+(I3) Loop 1= 12=(I1)5+(I2)4+10 Loop 2= (I3)2=10+(I2)4
0=-I1+I2+I3 0=(I1)5+(I2)4+10-12 0=10+(I2)4-(I3)2
[[-1 1 1] ^-1 [[ 0 ]
[ 5 4 0] x [ 2 ]
[ 0 4 -2]] [-10]]
But herein lies my problem, I have an HP 48GX, and it will not allow me to take the inverse of the first equation. I tried to take the inverse of each individual number as i entered it into the matrix, but the answer that i derived was not the same as those of my fellow classmates, all of whom are using TI 3600's. So how would i go about fixing this problem. And on a smaller note, is it possible to convert a decemile into a fraction? Thanx.

2. Mar 21, 2004

### nightwing

never mind, i just had to stop being a moron