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A level Maths OCR question help

i don't even know how to approach this question
Reply 1
Original post by esha06
i don't even know how to approach this question

Reply 2
Just think about the sin function.

50 the max height so ...

the wheel starts turning when t=0 so ...

One cycle takes 720s so ...

Its worth noting its in degrees.
Reply 3
Original post by mqb2766
Just think about the sin function.

50 the max height so ...

the wheel starts turning when t=0 so ...

One cycle takes 720s so ...

Its worth noting its in degrees.

i get what you're saying but how am I mean to know like which bit is what like what even is A
Reply 4
Original post by esha06
i get what you're saying but how am I mean to know like which bit is what like what even is A

It multplies/scales the output of the sin function. Really the question is asking about simple transformations, so A scales sin, b scales t and alpha is a translation (of bt)
Reply 5
Original post by mqb2766
It multplies/scales the output of the sin function. Really the question is asking about simple transformations, so A scales sin, b scales t and alpha is a translation (of bt)

so then because the maximum is 50 would A be 50 because the maximum of sin is 1
then to work out b and a is it something to do with 360 because that's one sin graph
Reply 6
Original post by esha06
so then because the maximum is 50 would A be 50 because the maximum of sin is 1
then to work out b and a is it something to do with 360 because that's one sin graph

Yes for A. Right idea for b, but you need to note that its the absolute value of sin as its
|Asin()|
so what is the period of that, and what must b be? The translation alpha is determined by the initial value as sin(0) = 0.
Reply 7
Original post by mqb2766
Yes for A. Right idea for b, but you need to note that its the absolute value of sin as its
|Asin()|
so what is the period of that, and what must b be? The translation alpha is determined by the initial value as sin(0) = 0.

oh so its 180 bc its not including negative values so the transformation from 180 to 720 is x4 so b would be 1/4 and then I can make H= 0 and use A and b to work out a
Reply 8
Original post by esha06
oh so its 180 bc its not including negative values so the transformation from 180 to 720 is x4 so b would be 1/4 and then I can make H= 0 and use A and b to work out a

For alpha (the simplest way), it would be when t=0 as that is the fact youre given. Then you dont need b (its the second fact) to work out alpha, you only need A (first fact).
(edited 6 months ago)
Reply 9
Original post by mqb2766
For alpha (the simplest way), it would be when t=0 as that is the fact youre given.

and make H=1?
Reply 10
Original post by esha06
and make H=1?

Yes, the fact says (t,H) = (0,1)
Reply 11
Original post by mqb2766
Yes, the fact says (t,H) = (0,1)

Right, thank you!!

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