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Graph This image is from my textbook.

In my textbook, there is one question: Does it makes sense to compute lim(T->50) R(T).

In this graph, I don't know lim is 1.5 or 0. Please tell me and explain for me, please.

thanks :)

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I think the limit from the left hand side is 0. – eccstartup Mar 16 '12 at 3:25
Can you explain why, please. I afraid that lim is 1,5 because when T= 50, it will be 0 – hqt Mar 16 '12 at 3:27
If T is continuous function, T must not have a straight line part parallel to the R axis. So I guess it is 0. – eccstartup Mar 16 '12 at 3:38
up vote 0 down vote accepted

This is a very bad textbook question. The graph of a function does not contain vertical lines. If the function is discontinuous at $50^\circ$, the graph merely jumps to a different value. Thus, if we take the graph literally, the seemingly vertical line at the end must be intended to be not quite vertical. Thus it would make sense to find $\lim_{T\to50^\circ}R(T)$, and it seems to be about $0.2$. However, I suspect that what they want you to say is that there's no such limit because $R$ is discontinuous at $50^\circ$. If so, that would be even worse.

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