Calle87
Need some help identifying the increase intervals of the graph of xtanx
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Calle87
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Venomblast
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is this in radian?
Calle87
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i know this is a even function about the y axis, and the domain and asymptotes are pi/2,-pi/2
Calle87
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just wondering how to show the intervals of increase and decrease
Venomblast
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so -90 degrees <x<90 degrees
Calle87
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usually i take f'x and solve for 0
Venomblast
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i see
Venomblast
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i see no 0. is this is an equation?
Calle87
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f'x=tanx+xsec^2x
Calle87
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@zepdrix hey do you think you could explain how they designate zero as a critical point?
Calle87
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Calle87
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should i just know that, from the x and y intercepts and the even symetry? and a basic knowledge of the tanx graph?
Calle87
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because when i set my derivative = 0 i have problems
zepdrix
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Hmm yah this derivative does seem to be putting up a fight :\
Hmmmmm
Calle87
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i tried changing everything to sines and cosines and still a mess
zepdrix
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Ah good call, I think that's how you find it! :)
The top is a big mess, yes.
But the bottom I think you can solve for a critical point.
Calle87
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Venomblast
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get the common denominator. so multiply cosx on the 1st term
Calle87
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thats it zep!!!!!!!!
Venomblast
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? zep?
Calle87
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@zepdrix :D
Venomblast
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i guess he/she got it from here
zepdrix
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Calle87
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i think the top should be ignored
Calle87
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the book doesent have a mention of it
Calle87
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neither does the graph
Calle87
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the only root is 0
Calle87
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maybe it would matter if the interval was larger than -pi/2,pi/2
zepdrix
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yah fair enough c:
zepdrix
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Hmmm wait what was I saying?
cos x = 0
Hmm that should give you x = pi/2 right?
why did i say it was x = 0?
Hmmmmmmmmmmmmmmmmm
Now I'm back to being confused about where the 0 critical point is coming from :D lol