malli07
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An objects displacement in metres at t seconds is given by the function: s= sin(2t)-t^3+4t^2+2
The input of the wine function is in degrees
A) Find the objects velocity at time t=0
B) Fund the objects acceleration at t=1
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mathstutor24
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Can you post your working so far and what you need help with please?
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malli07
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(Original post by mathstutor24)
Can you post your working so far and what you need help with please?
I don’t know how to go about it... the main struggle is to differentiate sin(2t)
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mathstutor24
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When differentiating sin(2t), you need differentiate it as if it was sin(u)(so this would be cos(u)) and then multiply it by the differentiation of "u" i.e. what is in the brackets.

So, if y=sin(2t)

then, \frac{dy}{dt}=2cos(2t)
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malli07
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(Original post by mathstutor24)
I've put together a graphic for you, as it's difficult to type everything here in code. Hope this helps:

Attachment 923796
Ok thank you 😃
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davros
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(Original post by mathstutor24)
When differentiating sin(2t), you need differentiate it as if it was sin(u)(so this would be cos(u)) and then multiply it by the differentiation of "u" i.e. what is in the brackets.

So, if y=sin(2t)

then, \frac{dy}{dt}=2cos(2t)
Note that according to the OP, the question states that: "The input of the wine function is in degrees" (sic)

This makes the differentiation "interesting"
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mathstutor24
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(Original post by davros)
Note that according to the OP, the question states that: "The input of the wine function is in degrees" (sic)

This makes the differentiation "interesting"
Must confess - did't read that bit

Just helping with basic differentiation of trig
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davros
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(Original post by mathstutor24)
Must confess - did't read that bit

Just helping with basic differentiation of trig
My point being: the derivative of sin x is only cos x provided that x is measured in radians...
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mathstutor24
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(Original post by davros)
My point being: the derivative of sin x is only cos x provided that x is measured in radians...
Thanks for pointing it out As I said, I missed that part of the question.

OP - do you need help differentiating in degrees, or are you okay with that bit?
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davros
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(Original post by mathstutor24)
Thanks for pointing it out As I said, I missed that part of the question.
Sorry - I wasn't trying to be 'sharp' by repeating myself. I re-read ,my original post and realised that you might have thought I was just drawing attention to the silly typo, so I thought I'd better add clarification

I wonder if this sort of question is going to arise more frequently - I know it's always been stated at A level that trig differentiation relies on radian measure, but I'm not sure if students are prepared to handle the adjustment needed if an independent variable is specified in degrees!
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mathstutor24
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(Original post by davros)
Sorry - I wasn't trying to be 'sharp' by repeating myself. I re-read ,my original post and realised that you might have thought I was just drawing attention to the silly typo, so I thought I'd better add clarification

I wonder if this sort of question is going to arise more frequently - I know it's always been stated at A level that trig differentiation relies on radian measure, but I'm not sure if students are prepared to handle the adjustment needed if an independent variable is specified in degrees!
No, no! I didn't think you were being sharp at all

I think differentiation of trig using degree measure is a good thing to be teaching. It's something that I can certainly see Edexcel sneakily throwing in, and as proved in this thread, it's really easy to overlook it and go ahead with "usual" differentiation (i.e. using radian measure).
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