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# C3 - Functions watch

1. Need some help with 9iii?
Do I put g(x) into f^-1(x) and see where it is not defined?
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2. (Original post by Super199)
Need some help with 9iii?
Do I put g(x) into f^-1(x) and see where it is not defined?
Yes
3. (Original post by Super199)
Need some help with 9iii?
Do I put g(x) into f^-1(x) and see where it is not defined?
Yes.
4. (Original post by TenOfThem)
Yes

(Original post by morgan8002)
Yes.
F^-1(x)= sin^-1(x/2)
So is it sin^-1[(4-2x^2)/2]
Where is it not defined? Not sure how you work that bit out
5. (Original post by Super199)
F^-1(x)= sin^-1(x/2)
So is it sin^-1[(4-2x^2)/2]
Where is it not defined? Not sure how you work that bit out
is undefined for
6. (Original post by Super199)
F^-1(x)= sin^-1(x/2)
So is it sin^-1[(4-2x^2)/2]
Where is it not defined? Not sure how you work that bit out
You can only take the arc sine of a value between -1 and 1
7. (Original post by morgan8002)
is undefined for
(Original post by TenOfThem)
You can only take the arc sine of a value between -1 and 1
So do I say it is undefined when (4-2x^2)/2 > 1 and (4-2x^2)/2 <-1?
8. (Original post by Super199)
So do I say it is undefined when (4-2x^2)/2 > 1 and (4-2x^2)/2 <-1?
You're on the right lines. You should work out the actual values of x that it is undefined for (solve each quadratic inequality).
9. (Original post by morgan8002)
You're on the right lines. You should work out the actual values of x that it is undefined for (solve each quadratic inequality).
Yeah got it. Cheers to you both
10. (Original post by morgan8002)
You're on the right lines. You should work out the actual values of x that it is undefined for (solve each quadratic inequality).
(Original post by TenOfThem)
You can only take the arc sine of a value between -1 and 1
Do you mind helping me with another question
Part 9ii.
http://www.ocr.org.uk/Images/144592-...hematics-3.pdf

I have to use part 1 but how?
I'm going to have a guess and say 6sin^2(1/2 theta)=2?
11. (Original post by Super199)
Do you mind helping me with another question
Part 9ii.
http://www.ocr.org.uk/Images/144592-...hematics-3.pdf

I have to use part 1 but how?
I'm going to have a guess and say 6sin^2(1/2 theta)=2?
Yes. Let . Then you can use the identity directly to obtain your guess.
12. (Original post by morgan8002)
Yes. Let . Then you can use the identity directly to obtain your guess.
Right done, how do you do the last part?
6sin^2(1/3theta)=k
How do I work out k if that is the right equation?
13. (Original post by Super199)
Right done, how do you do the last part?
6sin^2(1/3theta)=k
How do I work out k if that is the right equation?
k doesn't have a definite value. It has a range of possible values. The question asks for the set of possible values.

Therefore, you use the maximum and minimum values of in the given domain as the endpoints of the interval that k can be in.
14. (Original post by morgan8002)
k doesn't have a definite value. It has a range of possible values. The question asks for the set of possible values.

Therefore, you use the maximum and minimum values of in the given domain as the endpoints of the interval that k can be in.
Sorry but wh
(Original post by morgan8002)
k doesn't have a definite value. It has a range of possible values. The question asks for the set of possible values.

Therefore, you use the maximum and minimum values of in the given domain as the endpoints of the interval that k can be in.
mm I don't understand sorry
15. (Original post by Super199)
Sorry but wh
mm I don't understand sorry
k doesn't have one definite value. It can take a range of values, as the questions says. To find the range of values it can take the minimum is the minimum of in the given domain. The maximum value of k is the maximum of in the given domain.
16. (Original post by morgan8002)
k doesn't have one definite value. It can take a range of values, as the questions says. To find the range of values it can take the minimum is the minimum of in the given domain. The maximum value of k is the maximum of in the given domain.
Domain is -90< theta < 90?
Is the domain now -30< theta/3< 30?
I'm a bit lost
17. (Original post by Super199)
Domain is -90< theta < 90?
Is the domain now -30< theta/3< 30?
I'm a bit lost
Yes, that's right. So you need to find the values of in that give the maximum and minimum values of , and find these maximum and minimum values.
18. (Original post by morgan8002)
Yes, that's right. So you need to find the values of in that give the maximum and minimum values of , and find these maximum and minimum values.
Grr I have been an idiot. Done it! Thanks for the help
19. (Original post by Super199)
Grr I have been an idiot. Done it! Thanks for the help
No problem.

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