(New page: == LINEARITY == Linearity, in my definition, means that superposition always works. In other words, summation of inputs yield summation of outputs. == Example of Linearity and its proof ...)
 
m (Example of non-linearity and its proof)
 
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<math>x2(t) \to System \to y2(t)=x2(2t) \to Scalar multiplication(*b) \to bx2(2t) </math>
 
<math>x2(t) \to System \to y2(t)=x2(2t) \to Scalar multiplication(*b) \to bx2(2t) </math>
  
<math>ax1(2t) and bx2(2t) \to SUM \to '''ax1(2t)+bx2(2t)'''</math>
+
<math>ax1(2t) and bx2(2t) \to SUM \to ax1(2t)+bx2(2t)</math>
  
  
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<math>x2(t) \to Scalar multiplication(*b) \to bx2(t)</math>
 
<math>x2(t) \to Scalar multiplication(*b) \to bx2(t)</math>
  
<math>ax1(t) and bx2(t) \to SUM \to \to System \to'''ax1(2t)+bx2(2t)'''</math>
+
<math>ax1(t) and bx2(t) \to SUM \to \to System \to ax1(2t)+bx2(2t)</math>
  
 
Those two yielded the same outputs thus it is linear.
 
Those two yielded the same outputs thus it is linear.
 
  
 
== Example of non-linearity and its proof ==
 
== Example of non-linearity and its proof ==
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'''Proof:'''
 
'''Proof:'''
  
<math>x(t) \to System \to y(t)=e^{x(t)} \to Time Shift(t0) \to z(t)=y(t-t0)</math>
+
<math>x1(t) \to System \to y1(t)=e^{x1(t)} \to Scalar multiplication(*a) \to ae^{x1(t)} </math>
  
<math>\,                                                            =e^{x(t-t0)}\,</math>
+
<math>x2(t) \to System \to y2(t)=e^{x2(t)}\to Scalar multiplication(*b) \to be^{x2(t)} </math>
  
 +
<math>ae^{x1(t)} and be^{x2(t)} \to SUM \to ae^{x1(t)}+be^{x2(t)}</math>
  
  
<math>x(t) \to Time Shift(t0) \to y(t)=x(t-t0) \to System \to z(t)=e^{y(t)}</math>
 
  
<math>\,                                                            =e^{x(t-t0)}\,</math>
+
<math>x1(t) \to Scalar multiplication(*a) \to ax1(t)</math>
 +
 
 +
<math>x2(t) \to Scalar multiplication(*b) \to bx2(t)</math>
  
 +
<math>ax1(t) and bx2(t) \to SUM \to \to System \to e^{ax1(2t)+bx2(2t)}=e^{ax1(2t)}e^{bx2(2t)}</math>
  
Both cascades yielded the same outputs, thus <math>\,y(t)=e^{x(t)}\,</math> is time invariant.
+
Those two yielded different outputs, thus it is not linear.

Latest revision as of 16:53, 12 September 2008

LINEARITY

Linearity, in my definition, means that superposition always works. In other words, summation of inputs yield summation of outputs.

Example of Linearity and its proof

$ \,y(t)=x(2t)\, $


Proof:

$ x1(t) \to System \to y1(t)=x1(2t) \to Scalar multiplication(*a) \to ax1(2t) $

$ x2(t) \to System \to y2(t)=x2(2t) \to Scalar multiplication(*b) \to bx2(2t) $

$ ax1(2t) and bx2(2t) \to SUM \to ax1(2t)+bx2(2t) $


$ x1(t) \to Scalar multiplication(*a) \to ax1(t) $

$ x2(t) \to Scalar multiplication(*b) \to bx2(t) $

$ ax1(t) and bx2(t) \to SUM \to \to System \to ax1(2t)+bx2(2t) $

Those two yielded the same outputs thus it is linear.

Example of non-linearity and its proof

$ \,y(t)=e^{x(t)}\, $


Proof:

$ x1(t) \to System \to y1(t)=e^{x1(t)} \to Scalar multiplication(*a) \to ae^{x1(t)} $

$ x2(t) \to System \to y2(t)=e^{x2(t)}\to Scalar multiplication(*b) \to be^{x2(t)} $

$ ae^{x1(t)} and be^{x2(t)} \to SUM \to ae^{x1(t)}+be^{x2(t)} $


$ x1(t) \to Scalar multiplication(*a) \to ax1(t) $

$ x2(t) \to Scalar multiplication(*b) \to bx2(t) $

$ ax1(t) and bx2(t) \to SUM \to \to System \to e^{ax1(2t)+bx2(2t)}=e^{ax1(2t)}e^{bx2(2t)} $

Those two yielded different outputs, thus it is not linear.

Alumni Liaison

Abstract algebra continues the conceptual developments of linear algebra, on an even grander scale.

Dr. Paul Garrett