finding integral of $ sqrt {50-50cos(t)} $
$begingroup$
I have a cycloide
$ {x(t)=5 (t-sin(t)), y(t)=5(1-cos(t))} $ and
$ {x(t)=5 (t-sin(t)), y(t)=-5(1-cos(t))} $
and the aim is to find the circumference and to find it I have to show and take the differentiate integral:
$$ int sqrt{50-50cos(t)} dt $$
so I need help with it
Is the right anwser $ frac{-20}{sqrt{tan^2( frac{t}{2})+1}} $ ??
integration indefinite-integrals
$endgroup$
add a comment |
$begingroup$
I have a cycloide
$ {x(t)=5 (t-sin(t)), y(t)=5(1-cos(t))} $ and
$ {x(t)=5 (t-sin(t)), y(t)=-5(1-cos(t))} $
and the aim is to find the circumference and to find it I have to show and take the differentiate integral:
$$ int sqrt{50-50cos(t)} dt $$
so I need help with it
Is the right anwser $ frac{-20}{sqrt{tan^2( frac{t}{2})+1}} $ ??
integration indefinite-integrals
$endgroup$
$begingroup$
You should really add that $mathrm dt$ at the end.
$endgroup$
– Mohammad Zuhair Khan
Dec 5 '18 at 0:47
1
$begingroup$
Factor out $sqrt{50}$ and use my least favorite change of variables: $tan(t/2) = u.$
$endgroup$
– Sean Roberson
Dec 5 '18 at 0:49
add a comment |
$begingroup$
I have a cycloide
$ {x(t)=5 (t-sin(t)), y(t)=5(1-cos(t))} $ and
$ {x(t)=5 (t-sin(t)), y(t)=-5(1-cos(t))} $
and the aim is to find the circumference and to find it I have to show and take the differentiate integral:
$$ int sqrt{50-50cos(t)} dt $$
so I need help with it
Is the right anwser $ frac{-20}{sqrt{tan^2( frac{t}{2})+1}} $ ??
integration indefinite-integrals
$endgroup$
I have a cycloide
$ {x(t)=5 (t-sin(t)), y(t)=5(1-cos(t))} $ and
$ {x(t)=5 (t-sin(t)), y(t)=-5(1-cos(t))} $
and the aim is to find the circumference and to find it I have to show and take the differentiate integral:
$$ int sqrt{50-50cos(t)} dt $$
so I need help with it
Is the right anwser $ frac{-20}{sqrt{tan^2( frac{t}{2})+1}} $ ??
integration indefinite-integrals
integration indefinite-integrals
edited Dec 5 '18 at 1:13
Student123
asked Dec 5 '18 at 0:44
Student123Student123
536
536
$begingroup$
You should really add that $mathrm dt$ at the end.
$endgroup$
– Mohammad Zuhair Khan
Dec 5 '18 at 0:47
1
$begingroup$
Factor out $sqrt{50}$ and use my least favorite change of variables: $tan(t/2) = u.$
$endgroup$
– Sean Roberson
Dec 5 '18 at 0:49
add a comment |
$begingroup$
You should really add that $mathrm dt$ at the end.
$endgroup$
– Mohammad Zuhair Khan
Dec 5 '18 at 0:47
1
$begingroup$
Factor out $sqrt{50}$ and use my least favorite change of variables: $tan(t/2) = u.$
$endgroup$
– Sean Roberson
Dec 5 '18 at 0:49
$begingroup$
You should really add that $mathrm dt$ at the end.
$endgroup$
– Mohammad Zuhair Khan
Dec 5 '18 at 0:47
$begingroup$
You should really add that $mathrm dt$ at the end.
$endgroup$
– Mohammad Zuhair Khan
Dec 5 '18 at 0:47
1
1
$begingroup$
Factor out $sqrt{50}$ and use my least favorite change of variables: $tan(t/2) = u.$
$endgroup$
– Sean Roberson
Dec 5 '18 at 0:49
$begingroup$
Factor out $sqrt{50}$ and use my least favorite change of variables: $tan(t/2) = u.$
$endgroup$
– Sean Roberson
Dec 5 '18 at 0:49
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
$$sqrt{50-50cos x}=sqrt{50}sqrt{1 - cos x} =sqrt{50}sqrt{2 sin^2 frac{x} {2}}=10left| sinfrac{x} {2}right| $$
Can you finish now using this?
$endgroup$
$begingroup$
Did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
2
$begingroup$
Yes, your answer is correct. You can also simplify it to:$$frac{-20}{sqrt{tan^2 frac{t}{2}+1}} =frac{-20}{sqrt{sec^2 frac{t}{2}}} =-20left|cos frac{x} {2} right|$$ And of course you need to add $+C$. And if you differentiate it you should see that we find what I left in the answer.
$endgroup$
– Zacky
Dec 5 '18 at 1:20
$begingroup$
how did you simplify that?
$endgroup$
– Student123
Dec 5 '18 at 8:27
$begingroup$
Oh, I just realised that I used $x$ in the last part instead of $t$. To prove it I will denote $frac{t}{2}=z$ then we have: $$frac{1}{sqrt{tan^2 z+1}} =frac{1}{sqrt{frac{sin^2 z}{cos^2 z}+1}}=frac{1}{sqrt{frac{sin^2z+cos^2 z}{cos^2 z}}}=frac{1}{sqrt{frac{1}{cos^2 z}}} =sqrt{cos^2 z} =left|cos zright|$$ $$Rightarrow frac{-20}{sqrt{tan^2 frac{t}{2}+1}}=-20left|cos frac{t}{2} right|$$
$endgroup$
– Zacky
Dec 5 '18 at 9:52
$begingroup$
Something is wrong, because when I replace t from $ 2pi $ to 0, the circumference comes 0
$endgroup$
– Student123
Dec 6 '18 at 0:47
add a comment |
$begingroup$
Hint:
$$sqrt{50-50cos(t)}=sqrt{50}cdot sqrt{1-cos(t)}$$
and
$$sqrt{1-cos(t)}=sqrt{2}cdot|sin(t/2)| $$
$endgroup$
$begingroup$
did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
add a comment |
Your Answer
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2 Answers
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active
oldest
votes
2 Answers
2
active
oldest
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oldest
votes
$begingroup$
$$sqrt{50-50cos x}=sqrt{50}sqrt{1 - cos x} =sqrt{50}sqrt{2 sin^2 frac{x} {2}}=10left| sinfrac{x} {2}right| $$
Can you finish now using this?
$endgroup$
$begingroup$
Did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
2
$begingroup$
Yes, your answer is correct. You can also simplify it to:$$frac{-20}{sqrt{tan^2 frac{t}{2}+1}} =frac{-20}{sqrt{sec^2 frac{t}{2}}} =-20left|cos frac{x} {2} right|$$ And of course you need to add $+C$. And if you differentiate it you should see that we find what I left in the answer.
$endgroup$
– Zacky
Dec 5 '18 at 1:20
$begingroup$
how did you simplify that?
$endgroup$
– Student123
Dec 5 '18 at 8:27
$begingroup$
Oh, I just realised that I used $x$ in the last part instead of $t$. To prove it I will denote $frac{t}{2}=z$ then we have: $$frac{1}{sqrt{tan^2 z+1}} =frac{1}{sqrt{frac{sin^2 z}{cos^2 z}+1}}=frac{1}{sqrt{frac{sin^2z+cos^2 z}{cos^2 z}}}=frac{1}{sqrt{frac{1}{cos^2 z}}} =sqrt{cos^2 z} =left|cos zright|$$ $$Rightarrow frac{-20}{sqrt{tan^2 frac{t}{2}+1}}=-20left|cos frac{t}{2} right|$$
$endgroup$
– Zacky
Dec 5 '18 at 9:52
$begingroup$
Something is wrong, because when I replace t from $ 2pi $ to 0, the circumference comes 0
$endgroup$
– Student123
Dec 6 '18 at 0:47
add a comment |
$begingroup$
$$sqrt{50-50cos x}=sqrt{50}sqrt{1 - cos x} =sqrt{50}sqrt{2 sin^2 frac{x} {2}}=10left| sinfrac{x} {2}right| $$
Can you finish now using this?
$endgroup$
$begingroup$
Did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
2
$begingroup$
Yes, your answer is correct. You can also simplify it to:$$frac{-20}{sqrt{tan^2 frac{t}{2}+1}} =frac{-20}{sqrt{sec^2 frac{t}{2}}} =-20left|cos frac{x} {2} right|$$ And of course you need to add $+C$. And if you differentiate it you should see that we find what I left in the answer.
$endgroup$
– Zacky
Dec 5 '18 at 1:20
$begingroup$
how did you simplify that?
$endgroup$
– Student123
Dec 5 '18 at 8:27
$begingroup$
Oh, I just realised that I used $x$ in the last part instead of $t$. To prove it I will denote $frac{t}{2}=z$ then we have: $$frac{1}{sqrt{tan^2 z+1}} =frac{1}{sqrt{frac{sin^2 z}{cos^2 z}+1}}=frac{1}{sqrt{frac{sin^2z+cos^2 z}{cos^2 z}}}=frac{1}{sqrt{frac{1}{cos^2 z}}} =sqrt{cos^2 z} =left|cos zright|$$ $$Rightarrow frac{-20}{sqrt{tan^2 frac{t}{2}+1}}=-20left|cos frac{t}{2} right|$$
$endgroup$
– Zacky
Dec 5 '18 at 9:52
$begingroup$
Something is wrong, because when I replace t from $ 2pi $ to 0, the circumference comes 0
$endgroup$
– Student123
Dec 6 '18 at 0:47
add a comment |
$begingroup$
$$sqrt{50-50cos x}=sqrt{50}sqrt{1 - cos x} =sqrt{50}sqrt{2 sin^2 frac{x} {2}}=10left| sinfrac{x} {2}right| $$
Can you finish now using this?
$endgroup$
$$sqrt{50-50cos x}=sqrt{50}sqrt{1 - cos x} =sqrt{50}sqrt{2 sin^2 frac{x} {2}}=10left| sinfrac{x} {2}right| $$
Can you finish now using this?
answered Dec 5 '18 at 0:50
ZackyZacky
5,4981856
5,4981856
$begingroup$
Did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
2
$begingroup$
Yes, your answer is correct. You can also simplify it to:$$frac{-20}{sqrt{tan^2 frac{t}{2}+1}} =frac{-20}{sqrt{sec^2 frac{t}{2}}} =-20left|cos frac{x} {2} right|$$ And of course you need to add $+C$. And if you differentiate it you should see that we find what I left in the answer.
$endgroup$
– Zacky
Dec 5 '18 at 1:20
$begingroup$
how did you simplify that?
$endgroup$
– Student123
Dec 5 '18 at 8:27
$begingroup$
Oh, I just realised that I used $x$ in the last part instead of $t$. To prove it I will denote $frac{t}{2}=z$ then we have: $$frac{1}{sqrt{tan^2 z+1}} =frac{1}{sqrt{frac{sin^2 z}{cos^2 z}+1}}=frac{1}{sqrt{frac{sin^2z+cos^2 z}{cos^2 z}}}=frac{1}{sqrt{frac{1}{cos^2 z}}} =sqrt{cos^2 z} =left|cos zright|$$ $$Rightarrow frac{-20}{sqrt{tan^2 frac{t}{2}+1}}=-20left|cos frac{t}{2} right|$$
$endgroup$
– Zacky
Dec 5 '18 at 9:52
$begingroup$
Something is wrong, because when I replace t from $ 2pi $ to 0, the circumference comes 0
$endgroup$
– Student123
Dec 6 '18 at 0:47
add a comment |
$begingroup$
Did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
2
$begingroup$
Yes, your answer is correct. You can also simplify it to:$$frac{-20}{sqrt{tan^2 frac{t}{2}+1}} =frac{-20}{sqrt{sec^2 frac{t}{2}}} =-20left|cos frac{x} {2} right|$$ And of course you need to add $+C$. And if you differentiate it you should see that we find what I left in the answer.
$endgroup$
– Zacky
Dec 5 '18 at 1:20
$begingroup$
how did you simplify that?
$endgroup$
– Student123
Dec 5 '18 at 8:27
$begingroup$
Oh, I just realised that I used $x$ in the last part instead of $t$. To prove it I will denote $frac{t}{2}=z$ then we have: $$frac{1}{sqrt{tan^2 z+1}} =frac{1}{sqrt{frac{sin^2 z}{cos^2 z}+1}}=frac{1}{sqrt{frac{sin^2z+cos^2 z}{cos^2 z}}}=frac{1}{sqrt{frac{1}{cos^2 z}}} =sqrt{cos^2 z} =left|cos zright|$$ $$Rightarrow frac{-20}{sqrt{tan^2 frac{t}{2}+1}}=-20left|cos frac{t}{2} right|$$
$endgroup$
– Zacky
Dec 5 '18 at 9:52
$begingroup$
Something is wrong, because when I replace t from $ 2pi $ to 0, the circumference comes 0
$endgroup$
– Student123
Dec 6 '18 at 0:47
$begingroup$
Did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
$begingroup$
Did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
2
2
$begingroup$
Yes, your answer is correct. You can also simplify it to:$$frac{-20}{sqrt{tan^2 frac{t}{2}+1}} =frac{-20}{sqrt{sec^2 frac{t}{2}}} =-20left|cos frac{x} {2} right|$$ And of course you need to add $+C$. And if you differentiate it you should see that we find what I left in the answer.
$endgroup$
– Zacky
Dec 5 '18 at 1:20
$begingroup$
Yes, your answer is correct. You can also simplify it to:$$frac{-20}{sqrt{tan^2 frac{t}{2}+1}} =frac{-20}{sqrt{sec^2 frac{t}{2}}} =-20left|cos frac{x} {2} right|$$ And of course you need to add $+C$. And if you differentiate it you should see that we find what I left in the answer.
$endgroup$
– Zacky
Dec 5 '18 at 1:20
$begingroup$
how did you simplify that?
$endgroup$
– Student123
Dec 5 '18 at 8:27
$begingroup$
how did you simplify that?
$endgroup$
– Student123
Dec 5 '18 at 8:27
$begingroup$
Oh, I just realised that I used $x$ in the last part instead of $t$. To prove it I will denote $frac{t}{2}=z$ then we have: $$frac{1}{sqrt{tan^2 z+1}} =frac{1}{sqrt{frac{sin^2 z}{cos^2 z}+1}}=frac{1}{sqrt{frac{sin^2z+cos^2 z}{cos^2 z}}}=frac{1}{sqrt{frac{1}{cos^2 z}}} =sqrt{cos^2 z} =left|cos zright|$$ $$Rightarrow frac{-20}{sqrt{tan^2 frac{t}{2}+1}}=-20left|cos frac{t}{2} right|$$
$endgroup$
– Zacky
Dec 5 '18 at 9:52
$begingroup$
Oh, I just realised that I used $x$ in the last part instead of $t$. To prove it I will denote $frac{t}{2}=z$ then we have: $$frac{1}{sqrt{tan^2 z+1}} =frac{1}{sqrt{frac{sin^2 z}{cos^2 z}+1}}=frac{1}{sqrt{frac{sin^2z+cos^2 z}{cos^2 z}}}=frac{1}{sqrt{frac{1}{cos^2 z}}} =sqrt{cos^2 z} =left|cos zright|$$ $$Rightarrow frac{-20}{sqrt{tan^2 frac{t}{2}+1}}=-20left|cos frac{t}{2} right|$$
$endgroup$
– Zacky
Dec 5 '18 at 9:52
$begingroup$
Something is wrong, because when I replace t from $ 2pi $ to 0, the circumference comes 0
$endgroup$
– Student123
Dec 6 '18 at 0:47
$begingroup$
Something is wrong, because when I replace t from $ 2pi $ to 0, the circumference comes 0
$endgroup$
– Student123
Dec 6 '18 at 0:47
add a comment |
$begingroup$
Hint:
$$sqrt{50-50cos(t)}=sqrt{50}cdot sqrt{1-cos(t)}$$
and
$$sqrt{1-cos(t)}=sqrt{2}cdot|sin(t/2)| $$
$endgroup$
$begingroup$
did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
add a comment |
$begingroup$
Hint:
$$sqrt{50-50cos(t)}=sqrt{50}cdot sqrt{1-cos(t)}$$
and
$$sqrt{1-cos(t)}=sqrt{2}cdot|sin(t/2)| $$
$endgroup$
$begingroup$
did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
add a comment |
$begingroup$
Hint:
$$sqrt{50-50cos(t)}=sqrt{50}cdot sqrt{1-cos(t)}$$
and
$$sqrt{1-cos(t)}=sqrt{2}cdot|sin(t/2)| $$
$endgroup$
Hint:
$$sqrt{50-50cos(t)}=sqrt{50}cdot sqrt{1-cos(t)}$$
and
$$sqrt{1-cos(t)}=sqrt{2}cdot|sin(t/2)| $$
answered Dec 5 '18 at 0:52
Thomas ShelbyThomas Shelby
2,480221
2,480221
$begingroup$
did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
add a comment |
$begingroup$
did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
$begingroup$
did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
$begingroup$
did I get the right anwser?
$endgroup$
– Student123
Dec 5 '18 at 1:14
add a comment |
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$begingroup$
You should really add that $mathrm dt$ at the end.
$endgroup$
– Mohammad Zuhair Khan
Dec 5 '18 at 0:47
1
$begingroup$
Factor out $sqrt{50}$ and use my least favorite change of variables: $tan(t/2) = u.$
$endgroup$
– Sean Roberson
Dec 5 '18 at 0:49