• Congratulations to the Class of 2024 on your results!
    Let us know how you went here
    Got a question about your uni preferences? Ask us here

Sketch f(x) from f'(x) (1 Viewer)

_ShiFTy_

Member
Joined
Aug 7, 2005
Messages
185
Gender
Male
HSC
2006
From what i've gathered from doing one question, and looking at the answers...are these the main steps:

1) If the y = 0 , then stationarly point for f(x) curve
2) If stationairy point on f'(x) curve, then point of inflexion on f(x) curve?
3) If stationairy point AND y = 0 , then HORIZONTAL point of inflexion?

Is there anything else?
 
Last edited:

Riviet

.
Joined
Oct 11, 2005
Messages
5,593
Gender
Undisclosed
HSC
N/A
_ShiFTy_ said:
From what i've gathered from doing one question, and looking at the answers...are these the main steps:

1) If the y = 0 , then stationarly point for f(x) curve
2) If stationairy point on f'(x) curve, then point of inflexion on f(x) curve?
3) If stationairy point AND y = 0 , then HORIZONTAL point of inflexion?

Is there anything else?
Those seem right, you could also consider when the gradient goes from positive to negative, ie from above x axis, cutting the x axis, then going below the x axis, how fast it's increasing and decreasing.
 

_ShiFTy_

Member
Joined
Aug 7, 2005
Messages
185
Gender
Male
HSC
2006
Just thought of a few things. What if there was a vertical asymptote on the f'(x) curve? Would this just mean that the gradient will keep on increasing/decreasing so it would look parabolic or something?
And also, if there was a vertical tangent on an f(x) curve, what would it look like on the f'(x) curve?
 

Riviet

.
Joined
Oct 11, 2005
Messages
5,593
Gender
Undisclosed
HSC
N/A
_ShiFTy_ said:
Just thought of a few things. What if there was a vertical asymptote on the f'(x) curve? Would this just mean that the gradient will keep on increasing/decreasing so it would look parabolic or something?
And also, if there was a vertical tangent on an f(x) curve, what would it look like on the f'(x) curve?
If there was a vertical asymptote on the f ' (x) curve, then the original f(x) will also have the same vertical asymptote, since the gradient is increasing to infinity.
I'm not sure about the vertical tangent on an f(x) curve. I don't think this one is important since if there was a vertical tangent, then the curve would be a relation. :p
 

Sober

Member
Joined
Dec 6, 2005
Messages
215
Gender
Male
HSC
2003
_ShiFTy_ said:
Just thought of a few things. What if there was a vertical asymptote on the f'(x) curve? Would this just mean that the gradient will keep on increasing/decreasing so it would look parabolic or something?
And also, if there was a vertical tangent on an f(x) curve, what would it look like on the f'(x) curve?
I believe Riviet is incorrect. These two problems are actually the same thing and one implies the other.

Consider the function of a half circle, at the endpoints the gradient becomes vertical and the derivative is asymptopical at that point.
 

Riviet

.
Joined
Oct 11, 2005
Messages
5,593
Gender
Undisclosed
HSC
N/A
Sorry, wasn't thinking properly with the vertical tangents, of course the function could have a vertical tangent at its end point. :eek:
 

Sober

Member
Joined
Dec 6, 2005
Messages
215
Gender
Male
HSC
2003
Riviet said:
Sorry, wasn't thinking properly with the vertical tangents, of course the function could have a vertical tangent at its end point. :eek:
Not just the end point, consider f(x)=x1/3 ;)
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top