# Causality Question

1. Aug 8, 2008

### Schniz2

This is a question i asked my tutor via email... kind of in a hurry to get it answered so i can fully understand causality for an assignment due on monday.

i'm having trouble understanding the causality of the attached tutorial question...
if there is an input 'x(t)', for any 't<0' is this input zero? in the tutorial you wrote:
"say t < t1, x(t) = 0
lambda < t1, x(lambda) = 0
"
i'm not sure what you are referring to as 't1'... is this just an arbitrary time after 't = 0'? or is 't1' the origin of the input signal and any input signal before 't1' is zero.

if it is an arbitrary time after t = 0, how are we allowed to say that for 't < t1, x(t) = 0'?

Very grateful if anyone is able to help... cheers ;)

****Hmm, maybe this should have not been in this area... couldn't decide whether it was a homework question or just a question about the concept of causality :S****

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Last edited: Aug 8, 2008
2. Aug 16, 2008

### Conundrum

t1<x(t)
therefore
x(t)=0
t1 is the origin so this means it arbitrarily after 0

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