How do you decide what is dy/dt, or dx/dt

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Homework Help Overview

The discussion revolves around understanding the derivatives dy/dt and dx/dt in the context of finding dy/dx, given the equations y=2t+3 and x=t^2. Participants are exploring the relationships between these variables and the process of differentiation.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants are attempting to differentiate the equations with respect to t and are questioning how to interpret dy/dt and dx/dt. There is a focus on understanding the meaning of these derivatives and their application in finding dy/dx.

Discussion Status

The discussion is ongoing, with participants seeking clarification on the definitions and implications of dy/dt and dx/dt. Some guidance has been offered regarding the differentiation process, but there remains a lack of consensus on the conceptual understanding of these terms.

Contextual Notes

Participants express confusion regarding the textbook explanations of derivatives and their meanings, indicating a need for simpler interpretations. There is also a mention of the relationship between dependent and independent variables in differentiation.

AllanW
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Homework Statement


if y=2t+3 and x=t^2, find dy/dx

Homework Equations


dy=dy/dt*dt/dx

The Attempt at a Solution


dy/dt=2
dx/dt=2t
therefore dy/dx=1/t
what I don't understand is how the dy/dt etc. is found when attempting this problem[/B]
 
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AllanW said:

Homework Statement


if y=2t+3 and x=t^2, find dy/dx

Homework Equations


dy=dy/dt*dt/dx

The Attempt at a Solution


dy/dt=2
dx/dt=2t
therefore dy/dx=1/t
what I don't understand is how the dy/dt etc. is found when attempting this problem[/B]
Well, look at each equation in turn

The first equation is y = 2t + 3. What is dy/dt?

If this equation were written y = 2x + 3, would you have any problem finding dy/dx?

The second equation is x = t2

What if you wanted to find dy/dx for y = x2 ?

The rules of differentiation that you are supposed to learn are written around finding the change in the dependent variable with respect to the change in the independent variable. Since y is usually the dependent variable and x is the independent variable, the rules all state dy/dx = whatever.

For example, if y = xn, then dy/dx = n ⋅ xn-1
 
AllanW said:
what I don't understand is how the dy/dt etc. is found when attempting this problem
Do you know how to differentiate the formula 2t+3 with respect to t?
 
i understand differentiation in that you could find the derivative by going (2*1)t^(1-1) =2 I'm not clear on how it relates to dy/dt and combining it with dx/dt
 
i suppose what I am asking would be; what does dy/dt mean? I can't wrap my head around the explanation in my textbook and I am looking for a dumbed down version
 
AllanW said:
i suppose what I am asking would be; what does dy/dt mean
It is the rate of increase of y as t increases. Loosely put, it is the size of the tiny increase in y that would arise from making a tiny increase to t and putting that in the formula for y. If you do a line graph of y on the vertical axis against t on the horizontal axis it is the slope (gradient) of the line.
 

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