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C4 PPQ June 2008

Hey.
https://983c9f06eb1f75af6e83364e092b06f1cb5c4277.googledrive.com/host/0B1ZiqBksUHNYZzd2VHZlOXdqZlE/June%202008%20QP%20-%20C4%20OCR.pdf
Could somone explain question 9 (i) to be i was able to the a theta value for a by using the fact that DY/DX=0 as its a turning point but i dont see what to use for B.
Thanks
Reply 1
Avatar for Notnek
Notnek
21
Original post by SamuelN98
Hey.
https://983c9f06eb1f75af6e83364e092b06f1cb5c4277.googledrive.com/host/0B1ZiqBksUHNYZzd2VHZlOXdqZlE/June%202008%20QP%20-%20C4%20OCR.pdf
Could somone explain question 9 (i) to be i was able to the a theta value for a by using the fact that DY/DX=0 as its a turning point but i dont see what to use for B.
Thanks

At B, y = 0.

For A you don't need dy/dx, just use the fact that y is maximum at A and consider sin⁡θ\sin \theta.
(edited 8 years ago)
Reply 2
Avatar for SamuelN98
SamuelN98
OP
5
Original post by notnek
At B, y = 0.

For A you don't need dy/dx, just use the fact that y is maximum at A and consider sin⁡θ\sin \theta.


For B how do i determine which value of theta that makes sine(theta)=0 to use.
0, π\pi or 2 π\pi ?
(edited 8 years ago)
Reply 3
Avatar for Zacken
Zacken
22
Original post by SamuelN98
For B how do i determine which value of theta that makes sine(theta)=0 to use.
0,pie or 2 pie?


Well, you know it can't be 0 since that would make x be 0 as well. Now can you justify what it is between pi and 2pi using the position of A?
Reply 4
Avatar for Notnek
Notnek
21
Original post by SamuelN98
For B how do i determine which value of theta that makes sine(theta)=0 to use.
0,pie or 2 pie?

Plug these values of θ\theta into xx then determine which one of these coordinates must be B.

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