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avatar+1832 

How can I solve example 5.10 with out graphing

 Oct 12, 2014

Best Answer 

 #5
avatar+129852 
+10

I think the question is asking to evaluate the tan inverse as it approaches negative and positive infinity. And the questioner wants to know if this can be done without graphing.

And we want to know this:

lim  tan-1(x) as x→±∞

Let y= tan-1(x)

Then tan(y) = x

And as x → +∞, then y→ pi/2

Similarly, as x → -∞, then y → -pi/2

So, lim tan-1(x) as x→+∞  = pi/2  and lim tan-1(x) as x→-∞  = -pi/2

 

 Oct 12, 2014
 #1
avatar+118677 
+5

Sorry 315, besides the fact that it is late and my brain is shutting down.  My poor eyes really cannot read that. LOL

 Oct 12, 2014
 #2
avatar+1832 
0

No problem my instractor Help me when you are ready .. 

And I hope that I don't find this question in my quiz tomorrow =D 

 Oct 12, 2014
 #3
avatar+118677 
+5

What does the question say?

 Oct 12, 2014
 #5
avatar+129852 
+10
Best Answer

I think the question is asking to evaluate the tan inverse as it approaches negative and positive infinity. And the questioner wants to know if this can be done without graphing.

And we want to know this:

lim  tan-1(x) as x→±∞

Let y= tan-1(x)

Then tan(y) = x

And as x → +∞, then y→ pi/2

Similarly, as x → -∞, then y → -pi/2

So, lim tan-1(x) as x→+∞  = pi/2  and lim tan-1(x) as x→-∞  = -pi/2

 

CPhill Oct 12, 2014
 #6
avatar+1832 
0

ok thats well ! 

but you wrote that  (( And as x → +∞, then y→ pi/2 )) 

and I think it should be , when x → pi/2 , then y → +∞

 

right  ? 

 Oct 12, 2014
 #7
avatar+129852 
+5

Notice what I was evaluating when I wrote that.......it was...... tan(y) = x

And as x approaches infinity, y approaches pi/2.

If x just approaches pi/2, then y just approaches about 1. (in radians).

Graph the tangent inverse function......you will see that as x approaches infinity, y approaches pi/2 ... and as x approaches negative infinity, y approaches -pi/2.

 

 Oct 12, 2014
 #8
avatar+1832 
0

 

Nice, so my steps in answer must be like this? 

Also why we choose pi/2?  Why not  3pi/2 

 

 Oct 12, 2014
 #9
avatar+1832 
0

Are you here ?

 Oct 13, 2014
 #10
avatar+129852 
+5

Yeah...the steps look OK.

Remember that the "range" for the tangent inverse (i.e., the values returned by the function) are from -pi/2 to pi/2, exclusively. And -pi/2 and 3pi/2 are really the same coterminal angles.

 

 Oct 13, 2014

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