For real i have never found any maths tutorial so helpful but your videos are just great. Just got an A in my last mock on chapter 7 and 6 because of watching your tutorial. They are really helpful👍💯
@@zeeshanzamurred9280 For part C, I set 0.2t equal to what one revolution means (I.e. 2pi) and solved for t. I got the same answer. Can we use this method too?
its because there is a negative coefficient before cos, if you dont get it i recommend watching 7.5 (part 1) on zeeshans channel, he explains it pretty well.
Yeah so regardless if it -1 or 1 your main priority is to get the maximum value of the overall sum and the only way we do this is to sub in -1. If we subbed in 1 we would get an overall sum that is more negative than when we subbed in -1 to our equation. If we put these overall values on our cos graph it wouldnt really make sense if we put the more negative value higher than our more positive value on the y axis. I hope this makes sense
much easier method for part b, we know one complete revolution is the time required for 0.2t to change from 0 to 2pi, divide 2pi by 0.2 and you get 31 ur answer
@@Boomwhat-st5jw You might have got it already but remember with a cos graph to 3pi like he did, if you look at a cos graph and draw a straight line from -1 it will touch the cos graph at pi. the next time it will touch the graph will be at 3pi. Hope that helps
@@tasmins2406 when you get your cos-1(theta) then you subtract the answer from 2pi as it is the next rotation, then if you continue the process you will get 19.79 = 19.8
Hi Zeeshan, thanks for your wonderful videos. In 2022 paper 2 theres a Ferris wheel question where you have to find the complete trigonometric model. But this sort of modelling is no where taught in the spec. Where in the text book are these taught as you could actually have a chapter on it... This also goes for quadratic model type questions that have turned up in the exams. Do you have any videos or can point me towards any resources for these type of questions? Thank you.
For the finding the complete trignometric model, usually your given a value (such as the height of the ferris wheel originally), in which case you put the corresponding time into the equation. For example, Height of ferris wheel (H) = a - 10cos(10t) where t = time, and original height = 1m, then you know that at the original height time mjust be 0 as its just started, giving you the equation 1m = a - 10cos(10 * 0), allowing for you to solve the equation. I'm not sure if i've explained it well but it's basically what he did in this video but in reverse? sort of? you have the actual measurements and need to fill in the equation. :)
@@HamzaKhan0711 its the same method as the previous part. do inverse cos and you get two equations (0.2t+ 0.2985 = 2.027 and 0.2t + 0.2985 = 2π - 2.027) then you rearrange for t and get 8.6 and 19.8
So I'm assuming you managed to get 8.6? After that, the distance from 8.6 to the peak of the graph (14.2) is the same from the peak of the graph to t_2. So you would do 14.2-8.6 = 5.6 Now add 5.6 onto 14.2 because 5.6 is the distance between 14.2 and t_2. Which will give you 19.8
@@Ikiguyy nah i figured it out. What i think he meant was the time taken to reach 138m (the peak) was 14.2 seconds. he subtracted the time taken to reach the peak(14.2) from the time taken to reach only 100m(8.6). Which gave 5.6 seconds . Since the sine wave is symmetrical, to reach the next 100m apart from the first one you have to move for an extra 5.6seconds. Draw the sine wave and label it, it helps visualise what im trying to explain. by multiplying 5.6 twice to give (11.2) you have the total time it takes to get from one 100m to the next 100m. However since it took 8.6 seconds to get to the first 100m you have to add it to (11.2) which gives 19.8. Sry it kinda long tried to explain the best i could but if you rly wanna figure it out draw the graph and label the points.
You're a spectacular teacher!! Your explanations are really concise and succinct.
shush u neek
For real i have never found any maths tutorial so helpful but your videos are just great. Just got an A in my last mock on chapter 7 and 6 because of watching your tutorial. They are really helpful👍💯
my exams are next week and i just binged these. you really are going to be the reason i dont fail
Yhh I’m doing that now😭what grade did u get :))
@@estherkerr4773 i got a B
@@estherkerr4773 same, doing all the big stuff like trig, integration and differentiation
@@hasritha that’s so good well done. :)
Watched all chap 7 vids today haha, really awesome and detailed, so lucky that I am doing edexcel too
How did I just come across this video to realise these are the exact same questions i'm stuck on lmao
Lifesaver. My teacher didnt teach this clearly at all. You did.
Thank you for the vid, i never use to understand questions like c and d before 👍
I’m glad you found it useful 👍🏻
@@zeeshanzamurred9280 do we need to know about revolutions?
@@leahlester2620 yes it’s examinable. Just think about the periodicity of the sin and cos graph 👍🏻
@@zeeshanzamurred9280 For part C, I set 0.2t equal to what one revolution means (I.e. 2pi) and solved for t. I got the same answer. Can we use this method too?
Just recommended your channel to my whole class! Thanks for the videos, could u do some statistics and mechanics ones?
at 6:51 when you said that H is maximised when cos is minimised why is that the case? I thought that H should be maximised when cos is equal to 1
I have the same question ? Could someone explain pls?
its because there is a negative coefficient before cos, if you dont get it i recommend watching 7.5 (part 1) on zeeshans channel, he explains it pretty well.
why is the max of cos = -1, isn't it meant to be positive +1? - @6:53
8:38 - to maximise H, you need to minimise cos (because you need to make the negative into a positive)
Yeah so regardless if it -1 or 1 your main priority is to get the maximum value of the overall sum and the only way we do this is to sub in -1. If we subbed in 1 we would get an overall sum that is more negative than when we subbed in -1 to our equation. If we put these overall values on our cos graph it wouldnt really make sense if we put the more negative value higher than our more positive value on the y axis. I hope this makes sense
Why did you make it-1 to maximise
you kinda just do both and find which ones greater and take that as your max value
@ElkanaHagos-if8jbbecause if ur not adding or subtracting anything it wont be its largest/smallest possible value
Brilliant!
legend g, good stuff
much easier method for part b, we know one complete revolution is the time required for 0.2t to change from 0 to 2pi, divide 2pi by 0.2 and you get 31 ur answer
Top lad 👍
Thank you!
am i the onlny person stuck on how he got the second value for cos
have you found out? if so please tell me
@@HamzaKhan0711
cos(theta) = cos( theta - 360) I think but not too sure u might wanna research it
@@Boomwhat-st5jw You might have got it already but remember with a cos graph to 3pi like he did, if you look at a cos graph and draw a straight line from -1 it will touch the cos graph at pi. the next time it will touch the graph will be at 3pi. Hope that helps
@@danielmuriithi2298 can you please explain this further
@@tasmins2406 when you get your cos-1(theta) then you subtract the answer from 2pi as it is the next rotation, then if you continue the process you will get 19.79 = 19.8
this teacher deserves a knighthood
Life saver
Hi Zeeshan, thanks for your wonderful videos. In 2022 paper 2 theres a Ferris wheel question where you have to find the complete trigonometric model. But this sort of modelling is no where taught in the spec. Where in the text book are these taught as you could actually have a chapter on it... This also goes for quadratic model type questions that have turned up in the exams. Do you have any videos or can point me towards any resources for these type of questions? Thank you.
For the finding the complete trignometric model, usually your given a value (such as the height of the ferris wheel originally), in which case you put the corresponding time into the equation. For example, Height of ferris wheel (H) = a - 10cos(10t) where t = time, and original height = 1m, then you know that at the original height time mjust be 0 as its just started, giving you the equation 1m = a - 10cos(10 * 0), allowing for you to solve the equation. I'm not sure if i've explained it well but it's basically what he did in this video but in reverse? sort of? you have the actual measurements and need to fill in the equation. :)
@@lodhikids2965 thanks a lot. I really appreciate your help :)
How do you get R from square root of 65^2 + 20^2? How does it work?
R^2cos^2(alpha) + R^2sin^2(alpha). But you can factorise out the R^2. cos^2(alpha) + sin^2(alpha) =1. Therefore, R^2= 65^2 + 20^2
anyone know how he got 19.8 for the second value of t on part d
I'm confused on how he got 8.6 and 19.8, can anyone help me?
have you found out? if so please tell me
@@HamzaKhan0711 its the same method as the previous part. do inverse cos and you get two equations (0.2t+ 0.2985 = 2.027 and 0.2t + 0.2985 = 2π - 2.027) then you rearrange for t and get 8.6 and 19.8
How do you get 2 values of t?
So I'm assuming you managed to get 8.6? After that, the distance from 8.6 to the peak of the graph (14.2) is the same from the peak of the graph to t_2.
So you would do 14.2-8.6 = 5.6
Now add 5.6 onto 14.2 because 5.6 is the distance between 14.2 and t_2.
Which will give you 19.8
@@Ikiguyy I did it a different way I think but I don’t understand what you mean by the peak of the graph is 14.2, how did you get that?
@@Ikiguyy yh could you explain where you got 14.2 from?
@@Ikiguyy nah i figured it out. What i think he meant was the time taken to reach 138m (the peak) was 14.2 seconds. he subtracted the time taken to reach the peak(14.2) from the time taken to reach only 100m(8.6). Which gave 5.6 seconds .
Since the sine wave is symmetrical, to reach the next 100m apart from the first one you have to move for an extra 5.6seconds. Draw the sine wave and label it, it helps visualise what im trying to explain.
by multiplying 5.6 twice to give (11.2) you have the total time it takes to get from one 100m to the next 100m. However since it took 8.6 seconds to get to the first 100m you have to add it to (11.2) which gives 19.8.
Sry it kinda long tried to explain the best i could but if you rly wanna figure it out draw the graph and label the points.
@@Boomwhat-st5jw can u explain how he got t = 45.631 and t= 14.216 for part c