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# Maximum values question watch

1. What's the maximum value of 4-cos^2(x)?
Basically I need to know what the maximum value of cos^2(x) is!

Thank you
2. (Original post by Laurasage)
What's the maximum value of 4-cos^2(x)?
Basically I need to know what the maximum value of cos^2(x) is!

Thank you
Well, no, you need the minimum value of cos^2x since you are subtracting it

However ... The max or min of cos^2x is fairly obvious
3. (Original post by Laurasage)
What's the maximum value of 4-cos^2(x)?
Basically I need to know what the maximum value of cos^2(x) is!

Thank you
You need the minimum value of cos^2(x). Think about the range of cos(x) and hence the range of cos^2(x).
4. (Original post by TenOfThem)
Well, no, you need the minimum value of cos^2x since you are subtracting it

However ... The max or min of cos^2x is fairly obvious
Okay, yes that's true! Stupid of me... But could you tell me what it is please
5. (Original post by Laurasage)
Okay, yes that's true! Stupid of me... But could you tell me what it is please
Honestly .... Think a bit ... What values can cosx take .... When you square what values can it take
6. (Original post by SH0405)
You need the minimum value of cos^2(x). Think about the range of cos(x) and hence the range of cos^2(x).
Yes oops I've just realised that! Well the range of cos(x) is 1 to -1, is it the same?
7. (Original post by Laurasage)
Yes oops I've just realised that! Well the range of cos(x) is 1 to -1, is it the same?
Nope. 1 squared is 1, and -1 squared is 1. So the range of cos^2(x) is......?
8. (Original post by Laurasage)
Yes oops I've just realised that! Well the range of cos(x) is 1 to -1, is it the same?
Both of those square to give 1

You can get a smaller value
9. (Original post by SH0405)
Nope. 1 squared is 1, and -1 squared is 1. So the range of cos^2(x) is......?

(Original post by TenOfThem)
Both of those square to give 1

You can get a smaller value
0 to 1
Thank you both!
10. (Original post by Laurasage)
0 to 1
Thank you both!

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