Linear Systems

According to what I have understood, If a system input x(t) produces and output y(t), then it follows that if the system input is x(t+d) then output will be y(t+d). Also another idea is, If x1(t) --> y1(t) and x2(t) --> y2(t), then it follows that the input to the same system a1.x1(t)+a2.x2(t) gives output a1y1(t)+ a2y2(t)

Example of a Linear System

Given the system y(t) = 2x(t)

Input x1(t) = 4n and x2(t) = 10, we get y1(t) = 8n and y2(t) = 20. y1(t) + y2(t) = 8n+20

Input sum of the two inputs x(t) = 4n + 10, we get output y3(t) = 8n+20.

So--> y1(t) + y2(t) = y3(t) the system is LINEAR.

Example of Non-Linear System

GIVEN

x1(t) = t

x2(t) = t^2

y(t) = sin(x)

y1(t) = sin(t)

y2(t) = sin(t^2)

ay1 + by2 = a*sin(t) + b*sin(t^2) != Sin(ax1+bx2)

So Non-Linear.

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Prof. Math. Ohio State and Associate Dean
Outstanding Alumnus Purdue Math 2008

Jeff McNeal