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I have a question about radians vs degrees when determining a limit.
 2 years ago
 2 years ago
I have a question about radians vs degrees when determining a limit.
 2 years ago
 2 years ago

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keketsuBest ResponseYou've already chosen the best response.2
I'm working on the following limit: \[\lim_{x \rightarrow \pi} (\sin x/\sin x)\] I realize that this = 0, and that I need to use l'hopital's rule. My question is much simpler. This = 1 if I'm using degrees, but the correct answer of 0 (0/0) if I'm using radians. Would someone explain to me why I should be using radians?
 2 years ago

HermeezeyBest ResponseYou've already chosen the best response.1
yes because Pi is referring to the unit circle. The Sin graph itself is in Radians, because Radians are always written with Pi
 2 years ago

HermeezeyBest ResponseYou've already chosen the best response.1
I mean if you're dealing with Pi in trig, its a Radians problem
 2 years ago

PaxPolarisBest ResponseYou've already chosen the best response.0
Are you sure the right answer is 0?
 2 years ago

TuringTestBest ResponseYou've already chosen the best response.0
also \[0\neq\frac00\]
 2 years ago

keketsuBest ResponseYou've already chosen the best response.2
Hermeezey, perfect, thanks. That's the kind of thing I was looking for. So essentially, if I see a problem using pi, I need to be thinking radians, right? PaxPolaris, yeah, the problem comes with an answer. Because it comes out to 0/0, I need to find the derivative. So the ultimate answer isn't 0, but because the problem I listed comes out to 0, I need to take it further. Ah, TuringTest, I guess you're right. Infinity then?
 2 years ago

TuringTestBest ResponseYou've already chosen the best response.0
\[\frac00\]is what is called an indeterminate form. That means it's just not defined, as apposed to plus or minus infinity.
 2 years ago

TuringTestBest ResponseYou've already chosen the best response.0
In fact you can only use l'hospital's rule if by plugging in the value you are approaching you get one of the following indeterminate forms:\[\frac00\text{ or }\frac{\pm\infty}0\text{ or }\frac0{\pm\infty}\]if you had something that evaluated to\[\pm\infty\]for instance, using l'hospital is against the rules
 2 years ago

keketsuBest ResponseYou've already chosen the best response.2
Great. You're answering questions I didn't even know I had. :) Thanks all!
 2 years ago

keketsuBest ResponseYou've already chosen the best response.2
Nice, TuringTest. Thanks.
 2 years ago

PaxPolarisBest ResponseYou've already chosen the best response.0
\[\Large let\ f(x)= { \sin(x)\over \sin(x) }\] \[{\Large \therefore f(x) ={\cancel {\sin(x)}\over \cancel {\sin(x)}}= 1} ....except\ when\ \sin(x)\ is\ 0 \ where\ it\ is\ undefined\] as you cannot divide by 0 while f(π) is undefined,\[\Huge \lim_{x \rightarrow \pi}f(x)=1\]
 2 years ago
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