INFINITY GRADIENT ? A level edexcel maths help please C4 Watch

alevelhelpxoxo
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https://cdn.savemyexams.co.uk/wp-con...Maths-Pure.pdf

question 1 b
how are you meant to find the farthest point on a curve ? i cant find an example in my textbook to explain it to me
in the mark scheme it says to equal the derivative to infinity but why ?
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RDKGames
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(Original post by alevelhelpxoxo)
https://cdn.savemyexams.co.uk/wp-con...Maths-Pure.pdf

question 1 b
how are you meant to find the farthest point on a curve ? i cant find an example in my textbook to explain it to me
in the mark scheme it says to equal the derivative to infinity but why ?
Link does not work.
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alevelhelpxoxo
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(Original post by RDKGames)
Link does not work.
can you see it now ?
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bondangle
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It tells you the points furthest west and east respectively are P and Q. These have tangents at that point represented by the dotted line. If you cast your mind back to first doing gradients, a horizontal line has a gradient of 0 and the steeper it gets, the greater the gradient gets. However if you try calculate the gradient of a vertical line by conventional methods, you will find the for the y coordinate to increase the change in x is 0. So dy/dx has to be infinity as a straight vertical line represents an infinite gradient. If anymore help is needed or clarification on what I've said then feel free to ask, my explanation is a bit strange i admit.
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mqb2766
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The grad is infinite at these two points, so the denominator must be zero.
This gives a single equation in X and y.
Sub this into the equation of the ellipse to determine the value(s) of the variable(s).
Post your working if there is a problem.
(Original post by alevelhelpxoxo)
can you see it now ?
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alevelhelpxoxo
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(Original post by bondangle)
It tells you the points furthest west and east respectively are P and Q. These have tangents at that point represented by the dotted line. If you cast your mind back to first doing gradients, a horizontal line has a gradient of 0 and the steeper it gets, the greater the gradient gets. However if you try calculate the gradient of a vertical line by conventional methods, you will find the for the y coordinate to increase the change in x is 0. So dy/dx has to be infinity as a straight vertical line represents an infinite gradient. If anymore help is needed or clarification on what I've said then feel free to ask, my explanation is a bit strange i admit.
oh right I get it now thank you, I completely ignored the tangent. Also for part c when it asks to find the point furthermost north how would you go about that?
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mqb2766
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Gradient is zero, so the numerator is zero.
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alevelhelpxoxo
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why is it zero ?
(Original post by mqb2766)
Gradient is zero, so the numerator is zero.
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mqb2766
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That is the maximum.
(Original post by alevelhelpxoxo)
why is it zero ?
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DeadSilver
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So what you're basically saying is the 1/0 = infinity, right?
Anytime I mention that idea to my professor he thinks I've lost a screw.

(Original post by mqb2766)
The grad is infinite at these two points, so the denominator must be zero.
This gives a single equation in X and y.
Sub this into the equation of the ellipse to determine the value(s) of the variable(s).
Post your working if there is a problem.
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mqb2766
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Strictly speaking, divide by zero is undefined. In this case as the denominator approaches zero, the gradient increases without bound. So it approaches infinite.
Ask your prof what he/she means, if you domdo understand what they're saying?
(Original post by DeadSilver)
So what you're basically saying is the 1/0 = infinity, right?
Anytime I mention that idea to my professor he thinks I've lost a screw.
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DeadSilver
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Thanks, he's explained this before but I didn't understand it until now.
(Original post by mqb2766)
Strictly speaking, divide by zero is undefined. In this case as the denominator approaches zero, the gradient increases without bound. So it approaches infinite.
Ask your prof what he/she means, if you domdo understand what they're saying?
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Ahc1011
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All you do is dx/dy=0
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