#### MethMath11

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- Thread starter MethMath11
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\(\displaystyle x\in(a, b) \) means the same as \(\displaystyle a<x<b\).

Note one has square brackets and the other has round brackets to either include or exclude a and b.

It is used here as a way of stating the domain.

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Now that I know what it means. Sorry to bother you, is there any need for me to turn f(x) into an f'(x) in this question?\(\displaystyle x\in[a, b] \) means the same as \(\displaystyle a\leqx\leqb\).

\(\displaystyle x\in(a, b) \) means the same as \(\displaystyle a<x<b\).

Note one has square brackets and the other has round brackets to either include or exclude a and b.

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Define let (verb) in American English and get synonyms. What is let (verb)? let (verb) meaning, pronunciation and more by Macmillan Dictionary

www.macmillandictionary.com

5 [transitive] [usually in imperative] maths used in mathematics for saying that you are imagining that something is true, usually in order to prove a principle of mathematics

Let x = 5.

Let ABC be a triangle.

Here, it's the same idea, though not quite a definition: "Suppose that x is in the interval ...".

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I only know how to get the maximum number from a 1 trig, ex f(x) = cos2x or something like that, is there any link for me to study this equation?

\(\displaystyle x\in(a, b) \) means the same as \(\displaystyle a<x<b\).

Note one has square brackets and the other has round brackets to either include or exclude a and b.

It is used here as a way of stating the domain.

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You can find the max using calculus (ie finding f'(x)) OR by considering what the graph looks like.

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I took it that MethMath11 was asking what was meant by the symbolism after the "let".Letx = 4", or something like that, it means "Suppose thatx = 4". Literally, it can be thought of as "Make x be 4", that is, a definition of the variable. That's the closest to this usage I find in a dictionary, apart from this one that explicitly states the mathematical usage:

## let (verb) American English definition and synonyms | Macmillan Dictionary

Define let (verb) in American English and get synonyms. What is let (verb)? let (verb) meaning, pronunciation and more by Macmillan Dictionarywww.macmillandictionary.com5 [transitive] [usually in imperative] maths used in mathematics for saying that you are imagining that something is true, usually in order to prove a principle of mathematicsLet x = 5.Let ABC be a triangle.

Here, it's the same idea, though not quite a definition: "Suppose that x is in the interval ...".

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Sorry if I was being rude or something. But, could you please help me with this?You can find the max using calculus (ie finding f'(x)) OR by considering what the graph looks like.

I really have no idea what to do with the sec except turning it into a 1 + tan

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What formula are you asking about? If you're trying to list all points where cosine has its maximum, that's not going to help here, at least not yet. But since the problem is written in radians, you shouldn't be using degrees anyway.Can anyone help me with the formula, I forgot what sub-chapter the formula is,, but it's something like if it's cos, then the max is either at 90° or 270°, and then the formula is 90 = k.360 + x I think, can't remember it, can anyone help me?

What sec?? And I hope you aren't saying that sec x = 1 + tan x.I really have no idea what to do with the sec except turning it into a 1 + tan

As for solving the problem, one trick I see is to substitute x + pi/6 = u. That will at least make it a lot easier to work with the derivatives.

Please show what you've tried with the derivative (or any other method), so we can see what help you need.

On the other hand, are you allowed to use any tools such as a graphing calculator? Having checked the graph, I see that would save you a lot of work.

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It's sec^2 = 1+tan^2 xWhat formula are you asking about? If you're trying to list all points where cosine has its maximum, that's not going to help here, at least not yet. But since the problem is written in radians, you shouldn't be using degrees anyway.

What sec?? And I hope you aren't saying that sec x = 1 + tan x.

As for solving the problem, one trick I see is to substitute x + pi/6 = u. That will at least make it a lot easier to work with the derivatives.

Please show what you've tried with the derivative (or any other method), so we can see what help you need.

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Y' = sec^2 (x + 2π/3) - sec^2 ( x + π/6) - sin ( x + π/6What formula are you asking about? If you're trying to list all points where cosine has its maximum, that's not going to help here, at least not yet. But since the problem is written in radians, you shouldn't be using degrees anyway.

What sec?? And I hope you aren't saying that sec x = 1 + tan x.

As for solving the problem, one trick I see is to substitute x + pi/6 = u. That will at least make it a lot easier to work with the derivatives.

Please show what you've tried with the derivative (or any other method), so we can see what help you need.

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There's a problem with converting x + π/6 = u, how about the X +2π/3 ?

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What problem? Show your work!

If x + π/6 = u , then x = u - π/6. What is x + 2π/3 then?

If x + π/6 = u , then x = u - π/6. What is x + 2π/3 then?