How to find the range of a composite function?
$begingroup$
I have been stuck at this question: I have $$f(x)=cos(pi cdot x)$$$$g(x)=frac{7cdot x}{6}$$ and $$h(x)=f(g(x))$$
and i am asked to compute the range for $h(x)$.
My solution:
$$h(x)=cos(pi cdot frac{7x}{6})$$
so the highest value the function can output is $1$ and the lowest is $-1$. My instructor says it's not the right answer. How do i go about finding the range of this function? Thank you in advance.
EDIT
$f:mathbb{Q}tomathbb R$
$g:mathbb{Z}tomathbb{Q}$
functions
$endgroup$
add a comment |
$begingroup$
I have been stuck at this question: I have $$f(x)=cos(pi cdot x)$$$$g(x)=frac{7cdot x}{6}$$ and $$h(x)=f(g(x))$$
and i am asked to compute the range for $h(x)$.
My solution:
$$h(x)=cos(pi cdot frac{7x}{6})$$
so the highest value the function can output is $1$ and the lowest is $-1$. My instructor says it's not the right answer. How do i go about finding the range of this function? Thank you in advance.
EDIT
$f:mathbb{Q}tomathbb R$
$g:mathbb{Z}tomathbb{Q}$
functions
$endgroup$
2
$begingroup$
What is the domain?
$endgroup$
– Haris Gusic
7 hours ago
$begingroup$
You're only affecting the domain when you affect the input of a function. So your range should remain the same. I would imagine that you have a domain restriction as others have suggested...
$endgroup$
– Eleven-Eleven
7 hours ago
$begingroup$
ive updated the question you guys, this time i have included all information needed/given.
$endgroup$
– Reddevil
7 hours ago
2
$begingroup$
SInce you are only inputting integer values, you will not get a continuous range... You are only going to get specific outputs for integer inputs. This is because your angles are multiples of $7pi /6$
$endgroup$
– Eleven-Eleven
7 hours ago
add a comment |
$begingroup$
I have been stuck at this question: I have $$f(x)=cos(pi cdot x)$$$$g(x)=frac{7cdot x}{6}$$ and $$h(x)=f(g(x))$$
and i am asked to compute the range for $h(x)$.
My solution:
$$h(x)=cos(pi cdot frac{7x}{6})$$
so the highest value the function can output is $1$ and the lowest is $-1$. My instructor says it's not the right answer. How do i go about finding the range of this function? Thank you in advance.
EDIT
$f:mathbb{Q}tomathbb R$
$g:mathbb{Z}tomathbb{Q}$
functions
$endgroup$
I have been stuck at this question: I have $$f(x)=cos(pi cdot x)$$$$g(x)=frac{7cdot x}{6}$$ and $$h(x)=f(g(x))$$
and i am asked to compute the range for $h(x)$.
My solution:
$$h(x)=cos(pi cdot frac{7x}{6})$$
so the highest value the function can output is $1$ and the lowest is $-1$. My instructor says it's not the right answer. How do i go about finding the range of this function? Thank you in advance.
EDIT
$f:mathbb{Q}tomathbb R$
$g:mathbb{Z}tomathbb{Q}$
functions
functions
edited 7 hours ago
Lemniscate
402211
402211
asked 7 hours ago
ReddevilReddevil
11718
11718
2
$begingroup$
What is the domain?
$endgroup$
– Haris Gusic
7 hours ago
$begingroup$
You're only affecting the domain when you affect the input of a function. So your range should remain the same. I would imagine that you have a domain restriction as others have suggested...
$endgroup$
– Eleven-Eleven
7 hours ago
$begingroup$
ive updated the question you guys, this time i have included all information needed/given.
$endgroup$
– Reddevil
7 hours ago
2
$begingroup$
SInce you are only inputting integer values, you will not get a continuous range... You are only going to get specific outputs for integer inputs. This is because your angles are multiples of $7pi /6$
$endgroup$
– Eleven-Eleven
7 hours ago
add a comment |
2
$begingroup$
What is the domain?
$endgroup$
– Haris Gusic
7 hours ago
$begingroup$
You're only affecting the domain when you affect the input of a function. So your range should remain the same. I would imagine that you have a domain restriction as others have suggested...
$endgroup$
– Eleven-Eleven
7 hours ago
$begingroup$
ive updated the question you guys, this time i have included all information needed/given.
$endgroup$
– Reddevil
7 hours ago
2
$begingroup$
SInce you are only inputting integer values, you will not get a continuous range... You are only going to get specific outputs for integer inputs. This is because your angles are multiples of $7pi /6$
$endgroup$
– Eleven-Eleven
7 hours ago
2
2
$begingroup$
What is the domain?
$endgroup$
– Haris Gusic
7 hours ago
$begingroup$
What is the domain?
$endgroup$
– Haris Gusic
7 hours ago
$begingroup$
You're only affecting the domain when you affect the input of a function. So your range should remain the same. I would imagine that you have a domain restriction as others have suggested...
$endgroup$
– Eleven-Eleven
7 hours ago
$begingroup$
You're only affecting the domain when you affect the input of a function. So your range should remain the same. I would imagine that you have a domain restriction as others have suggested...
$endgroup$
– Eleven-Eleven
7 hours ago
$begingroup$
ive updated the question you guys, this time i have included all information needed/given.
$endgroup$
– Reddevil
7 hours ago
$begingroup$
ive updated the question you guys, this time i have included all information needed/given.
$endgroup$
– Reddevil
7 hours ago
2
2
$begingroup$
SInce you are only inputting integer values, you will not get a continuous range... You are only going to get specific outputs for integer inputs. This is because your angles are multiples of $7pi /6$
$endgroup$
– Eleven-Eleven
7 hours ago
$begingroup$
SInce you are only inputting integer values, you will not get a continuous range... You are only going to get specific outputs for integer inputs. This is because your angles are multiples of $7pi /6$
$endgroup$
– Eleven-Eleven
7 hours ago
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
Your composite function then is
$$fcirc g:mathbb{Z}rightarrow mathbb{R}$$
But now, by inputting only multiples of $frac{7pi}{6}$ into the cosine function, and because cosine is a periodic function, you are only going to get specific values for your range. These are your "special" angle values because you will never have an angle as an input to cosine that is NOT a multiple of $frac{pi}{6}$. So your range will be $$left{-1,-frac{sqrt{3}}{2},-frac{1}{2},0,frac{1}{2},frac{sqrt{3}}{2},1right}$$
$endgroup$
add a comment |
$begingroup$
Since $f(x) = cos(pi x)$ has periodicity $2$, we have $h(x) = f(g(x)) = f(frac{7x}{6}+2m)$ with $m$ integer. Now note that $h(x)=h(x+12)$.
Thus your codomain will be determined by $xin{0,1,dots,11}$. The range is then determined by the unique subset of values from ${h(0),h(1),dots,h(11)}$.
$endgroup$
add a comment |
$begingroup$
Normally range is taken to mean the image (set of possible outputs). Perhaps I'm wrong but you seem to want to know the global minimum and global maximum of $h$. The global minimum of $h$ is $-1$ and the global maximum is $1$.
$h(12) = mathrm{cos}(14 pi) = 1$, and $h(6) = mathrm{cos}(7 pi) = -1$.
Since $forall x in mathbb{R}$ $mathrm{cos}(x) in [-1,1]$, we have $forall x in mathbb{Q}$ $f(x) in [-1,1]$. This means that $h$ does not take values above $1$ or below $-1$.
$endgroup$
$begingroup$
You are wrong. It doesnt extend above or below 1 or -1 but it doesnt map to everything between 1 and -1 . Maybe you got confused by range en.m.wikipedia.org/wiki/Range_(mathematics)
$endgroup$
– Milan Stojanovic
7 hours ago
$begingroup$
Yes, I was unclear about what I meant. @Reddevil talks about the highest and lowest values and so I have addressed that.
$endgroup$
– Lemniscate
7 hours ago
add a comment |
Your Answer
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Your composite function then is
$$fcirc g:mathbb{Z}rightarrow mathbb{R}$$
But now, by inputting only multiples of $frac{7pi}{6}$ into the cosine function, and because cosine is a periodic function, you are only going to get specific values for your range. These are your "special" angle values because you will never have an angle as an input to cosine that is NOT a multiple of $frac{pi}{6}$. So your range will be $$left{-1,-frac{sqrt{3}}{2},-frac{1}{2},0,frac{1}{2},frac{sqrt{3}}{2},1right}$$
$endgroup$
add a comment |
$begingroup$
Your composite function then is
$$fcirc g:mathbb{Z}rightarrow mathbb{R}$$
But now, by inputting only multiples of $frac{7pi}{6}$ into the cosine function, and because cosine is a periodic function, you are only going to get specific values for your range. These are your "special" angle values because you will never have an angle as an input to cosine that is NOT a multiple of $frac{pi}{6}$. So your range will be $$left{-1,-frac{sqrt{3}}{2},-frac{1}{2},0,frac{1}{2},frac{sqrt{3}}{2},1right}$$
$endgroup$
add a comment |
$begingroup$
Your composite function then is
$$fcirc g:mathbb{Z}rightarrow mathbb{R}$$
But now, by inputting only multiples of $frac{7pi}{6}$ into the cosine function, and because cosine is a periodic function, you are only going to get specific values for your range. These are your "special" angle values because you will never have an angle as an input to cosine that is NOT a multiple of $frac{pi}{6}$. So your range will be $$left{-1,-frac{sqrt{3}}{2},-frac{1}{2},0,frac{1}{2},frac{sqrt{3}}{2},1right}$$
$endgroup$
Your composite function then is
$$fcirc g:mathbb{Z}rightarrow mathbb{R}$$
But now, by inputting only multiples of $frac{7pi}{6}$ into the cosine function, and because cosine is a periodic function, you are only going to get specific values for your range. These are your "special" angle values because you will never have an angle as an input to cosine that is NOT a multiple of $frac{pi}{6}$. So your range will be $$left{-1,-frac{sqrt{3}}{2},-frac{1}{2},0,frac{1}{2},frac{sqrt{3}}{2},1right}$$
edited 7 hours ago
answered 7 hours ago
Eleven-ElevenEleven-Eleven
5,71072759
5,71072759
add a comment |
add a comment |
$begingroup$
Since $f(x) = cos(pi x)$ has periodicity $2$, we have $h(x) = f(g(x)) = f(frac{7x}{6}+2m)$ with $m$ integer. Now note that $h(x)=h(x+12)$.
Thus your codomain will be determined by $xin{0,1,dots,11}$. The range is then determined by the unique subset of values from ${h(0),h(1),dots,h(11)}$.
$endgroup$
add a comment |
$begingroup$
Since $f(x) = cos(pi x)$ has periodicity $2$, we have $h(x) = f(g(x)) = f(frac{7x}{6}+2m)$ with $m$ integer. Now note that $h(x)=h(x+12)$.
Thus your codomain will be determined by $xin{0,1,dots,11}$. The range is then determined by the unique subset of values from ${h(0),h(1),dots,h(11)}$.
$endgroup$
add a comment |
$begingroup$
Since $f(x) = cos(pi x)$ has periodicity $2$, we have $h(x) = f(g(x)) = f(frac{7x}{6}+2m)$ with $m$ integer. Now note that $h(x)=h(x+12)$.
Thus your codomain will be determined by $xin{0,1,dots,11}$. The range is then determined by the unique subset of values from ${h(0),h(1),dots,h(11)}$.
$endgroup$
Since $f(x) = cos(pi x)$ has periodicity $2$, we have $h(x) = f(g(x)) = f(frac{7x}{6}+2m)$ with $m$ integer. Now note that $h(x)=h(x+12)$.
Thus your codomain will be determined by $xin{0,1,dots,11}$. The range is then determined by the unique subset of values from ${h(0),h(1),dots,h(11)}$.
edited 7 hours ago
answered 7 hours ago
zahbazzahbaz
8,38921937
8,38921937
add a comment |
add a comment |
$begingroup$
Normally range is taken to mean the image (set of possible outputs). Perhaps I'm wrong but you seem to want to know the global minimum and global maximum of $h$. The global minimum of $h$ is $-1$ and the global maximum is $1$.
$h(12) = mathrm{cos}(14 pi) = 1$, and $h(6) = mathrm{cos}(7 pi) = -1$.
Since $forall x in mathbb{R}$ $mathrm{cos}(x) in [-1,1]$, we have $forall x in mathbb{Q}$ $f(x) in [-1,1]$. This means that $h$ does not take values above $1$ or below $-1$.
$endgroup$
$begingroup$
You are wrong. It doesnt extend above or below 1 or -1 but it doesnt map to everything between 1 and -1 . Maybe you got confused by range en.m.wikipedia.org/wiki/Range_(mathematics)
$endgroup$
– Milan Stojanovic
7 hours ago
$begingroup$
Yes, I was unclear about what I meant. @Reddevil talks about the highest and lowest values and so I have addressed that.
$endgroup$
– Lemniscate
7 hours ago
add a comment |
$begingroup$
Normally range is taken to mean the image (set of possible outputs). Perhaps I'm wrong but you seem to want to know the global minimum and global maximum of $h$. The global minimum of $h$ is $-1$ and the global maximum is $1$.
$h(12) = mathrm{cos}(14 pi) = 1$, and $h(6) = mathrm{cos}(7 pi) = -1$.
Since $forall x in mathbb{R}$ $mathrm{cos}(x) in [-1,1]$, we have $forall x in mathbb{Q}$ $f(x) in [-1,1]$. This means that $h$ does not take values above $1$ or below $-1$.
$endgroup$
$begingroup$
You are wrong. It doesnt extend above or below 1 or -1 but it doesnt map to everything between 1 and -1 . Maybe you got confused by range en.m.wikipedia.org/wiki/Range_(mathematics)
$endgroup$
– Milan Stojanovic
7 hours ago
$begingroup$
Yes, I was unclear about what I meant. @Reddevil talks about the highest and lowest values and so I have addressed that.
$endgroup$
– Lemniscate
7 hours ago
add a comment |
$begingroup$
Normally range is taken to mean the image (set of possible outputs). Perhaps I'm wrong but you seem to want to know the global minimum and global maximum of $h$. The global minimum of $h$ is $-1$ and the global maximum is $1$.
$h(12) = mathrm{cos}(14 pi) = 1$, and $h(6) = mathrm{cos}(7 pi) = -1$.
Since $forall x in mathbb{R}$ $mathrm{cos}(x) in [-1,1]$, we have $forall x in mathbb{Q}$ $f(x) in [-1,1]$. This means that $h$ does not take values above $1$ or below $-1$.
$endgroup$
Normally range is taken to mean the image (set of possible outputs). Perhaps I'm wrong but you seem to want to know the global minimum and global maximum of $h$. The global minimum of $h$ is $-1$ and the global maximum is $1$.
$h(12) = mathrm{cos}(14 pi) = 1$, and $h(6) = mathrm{cos}(7 pi) = -1$.
Since $forall x in mathbb{R}$ $mathrm{cos}(x) in [-1,1]$, we have $forall x in mathbb{Q}$ $f(x) in [-1,1]$. This means that $h$ does not take values above $1$ or below $-1$.
edited 7 hours ago
answered 7 hours ago
LemniscateLemniscate
402211
402211
$begingroup$
You are wrong. It doesnt extend above or below 1 or -1 but it doesnt map to everything between 1 and -1 . Maybe you got confused by range en.m.wikipedia.org/wiki/Range_(mathematics)
$endgroup$
– Milan Stojanovic
7 hours ago
$begingroup$
Yes, I was unclear about what I meant. @Reddevil talks about the highest and lowest values and so I have addressed that.
$endgroup$
– Lemniscate
7 hours ago
add a comment |
$begingroup$
You are wrong. It doesnt extend above or below 1 or -1 but it doesnt map to everything between 1 and -1 . Maybe you got confused by range en.m.wikipedia.org/wiki/Range_(mathematics)
$endgroup$
– Milan Stojanovic
7 hours ago
$begingroup$
Yes, I was unclear about what I meant. @Reddevil talks about the highest and lowest values and so I have addressed that.
$endgroup$
– Lemniscate
7 hours ago
$begingroup$
You are wrong. It doesnt extend above or below 1 or -1 but it doesnt map to everything between 1 and -1 . Maybe you got confused by range en.m.wikipedia.org/wiki/Range_(mathematics)
$endgroup$
– Milan Stojanovic
7 hours ago
$begingroup$
You are wrong. It doesnt extend above or below 1 or -1 but it doesnt map to everything between 1 and -1 . Maybe you got confused by range en.m.wikipedia.org/wiki/Range_(mathematics)
$endgroup$
– Milan Stojanovic
7 hours ago
$begingroup$
Yes, I was unclear about what I meant. @Reddevil talks about the highest and lowest values and so I have addressed that.
$endgroup$
– Lemniscate
7 hours ago
$begingroup$
Yes, I was unclear about what I meant. @Reddevil talks about the highest and lowest values and so I have addressed that.
$endgroup$
– Lemniscate
7 hours ago
add a comment |
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2
$begingroup$
What is the domain?
$endgroup$
– Haris Gusic
7 hours ago
$begingroup$
You're only affecting the domain when you affect the input of a function. So your range should remain the same. I would imagine that you have a domain restriction as others have suggested...
$endgroup$
– Eleven-Eleven
7 hours ago
$begingroup$
ive updated the question you guys, this time i have included all information needed/given.
$endgroup$
– Reddevil
7 hours ago
2
$begingroup$
SInce you are only inputting integer values, you will not get a continuous range... You are only going to get specific outputs for integer inputs. This is because your angles are multiples of $7pi /6$
$endgroup$
– Eleven-Eleven
7 hours ago