(Example of non-linearity and its proof)
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<math>x2(t) \to System \to y2(t)=e^{x2(t)}\to Scalar multiplication(*b) \to be^{x2(t)} </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)} & be^{x2(t)} \to SUM \to ae^{x1(t)}+be^{x2(t)}</math>
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<math>ae^{x1(t)} and be^{x2(t)} \to SUM \to ae^{x1(t)}+be^{x2(t)}</math>
  
  
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<math>ax1(t) and bx2(t) \to SUM \to \to System \to e^{ax1(2t)+bx2(2t)}=e^{ax1(2t)}e^{bx2(2t)}</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>
  
Those two yielded the same outputs thus it is linear.
+
Those two yielded different outputs, thus it is not linear.

Latest revision as of 17:53, 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

Ph.D. 2007, working on developing cool imaging technologies for digital cameras, camera phones, and video surveillance cameras.

Buyue Zhang