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# Can I use dy/dx instead of a tangent on velocity time graphs? watch

1. I learnt differentiation from Add Maths, so would I be able to get full marks on a question where you're supposed to use a tangent to find the gradient of a curve on a velocity time graph if I used differentiation?
2. (Original post by Astravolt)
I learnt differentiation from Add Maths, so would I be able to get full marks on a question where you're supposed to use a tangent to find the gradient of a curve on a velocity time graph if I used differentiation?
3. (Original post by Astravolt)
I learnt differentiation from Add Maths, so would I be able to get full marks on a question where you're supposed to use a tangent to find the gradient of a curve on a velocity time graph if I used differentiation?
Most of the time when they give you a velocity time graph, they won't give a function, only the line itself. So there will be no function to differentiate and you will have to draw a tangent.
4. Differentiation requires you to know the equation of the line (e.g. y = 2x +5) and is usually not provided in velocity-time graph related questions. Therefore you need to take a tangent instead.
5. Sorry, I got mixed up between velocity time graphs and gradients of curves! An example question is "The graph of y = x^3 - 2x is shown below, estimate the gradient of the graph at x = -1". I used differentiation to get 1 as the gradient, which is the same as the answer on the mark scheme, so do you think I would be able to get full marks on that using differentiation?
6. (Original post by Astravolt)
Sorry, I got mixed up between velocity time graphs and gradients of curves! An example question is "The graph of y = x^3 - 2x is shown below, estimate the gradient of the graph at x = -1". I used differentiation to get 1 as the gradient, which is the same as the answer on the mark scheme, so do you think I would be able to get full marks on that using differentiation?
As it says estimate they would want to see your workings so you may get 1 mark for the right answer but you haven't obtained your answer in the correct way.
7. (Original post by Astravolt)
Sorry, I got mixed up between velocity time graphs and gradients of curves! An example question is "The graph of y = x^3 - 2x is shown below, estimate the gradient of the graph at x = -1". I used differentiation to get 1 as the gradient, which is the same as the answer on the mark scheme, so do you think I would be able to get full marks on that using differentiation?
You may or may not get any marks (more likely not). The question says estimate so they expect you to draw a tangent. You can use differentiation to check your answer, which is very useful for a question like this.

For all questions I recommend avoiding using any maths that is beyond the spec. It's not worth risking it even if you feel that a question can be done in a quicker way using higher level maths.
8. (Original post by Charliewiz)
As it says estimate they would want to see your workings so you may get 1 mark for the right answer but you haven't obtained your answer in the correct way.
(Original post by Notnek)
You may or may not get any marks (more likely not). The question says estimate so they expect you to draw a tangent. You can use differentiation to check your answer, which is very useful for a question like this.

For all questions I recommend avoiding using any maths that is beyond the spec. It's not worth risking it even if you feel that a question can be done in a quicker way using higher level maths.
Okay then, at least I can use it to check my answer, thanks!

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