Tangent line to parametric curve at a point
Consider the curve given parametrically by $(x,y,z)=(2−t,−1−t^2,−2t−3t^3)$. There is a unique point $P$ on the curve with the property that the tangent line at $P$ passes through the point $(2,8,−162)$. Find the coordinates of the point $P$.
Can anyone give me a hand with this one? I honestly have no idea where to start other than rewriting the curve as,
$vec{r(t)}$ = $langle 2-t, -1-t^2, -2t-3t^3rangle$, and then taking the derivate to obtain,
$vec{r'(t)}$ = $langle -1, -2t, -2 -9t^2rangle$
parametric tangent-line
add a comment |
Consider the curve given parametrically by $(x,y,z)=(2−t,−1−t^2,−2t−3t^3)$. There is a unique point $P$ on the curve with the property that the tangent line at $P$ passes through the point $(2,8,−162)$. Find the coordinates of the point $P$.
Can anyone give me a hand with this one? I honestly have no idea where to start other than rewriting the curve as,
$vec{r(t)}$ = $langle 2-t, -1-t^2, -2t-3t^3rangle$, and then taking the derivate to obtain,
$vec{r'(t)}$ = $langle -1, -2t, -2 -9t^2rangle$
parametric tangent-line
What is an equation of the tangent line at $r(t)$? What does it mean in terms of this equation for $(2,8,-162)$ to be on this line?
– amd
May 19 '17 at 1:22
Managed to figure it out getting P equal to (5,-10,87). Thanks.
– John
May 19 '17 at 1:31
add a comment |
Consider the curve given parametrically by $(x,y,z)=(2−t,−1−t^2,−2t−3t^3)$. There is a unique point $P$ on the curve with the property that the tangent line at $P$ passes through the point $(2,8,−162)$. Find the coordinates of the point $P$.
Can anyone give me a hand with this one? I honestly have no idea where to start other than rewriting the curve as,
$vec{r(t)}$ = $langle 2-t, -1-t^2, -2t-3t^3rangle$, and then taking the derivate to obtain,
$vec{r'(t)}$ = $langle -1, -2t, -2 -9t^2rangle$
parametric tangent-line
Consider the curve given parametrically by $(x,y,z)=(2−t,−1−t^2,−2t−3t^3)$. There is a unique point $P$ on the curve with the property that the tangent line at $P$ passes through the point $(2,8,−162)$. Find the coordinates of the point $P$.
Can anyone give me a hand with this one? I honestly have no idea where to start other than rewriting the curve as,
$vec{r(t)}$ = $langle 2-t, -1-t^2, -2t-3t^3rangle$, and then taking the derivate to obtain,
$vec{r'(t)}$ = $langle -1, -2t, -2 -9t^2rangle$
parametric tangent-line
parametric tangent-line
asked May 19 '17 at 1:07
JohnJohn
549
549
What is an equation of the tangent line at $r(t)$? What does it mean in terms of this equation for $(2,8,-162)$ to be on this line?
– amd
May 19 '17 at 1:22
Managed to figure it out getting P equal to (5,-10,87). Thanks.
– John
May 19 '17 at 1:31
add a comment |
What is an equation of the tangent line at $r(t)$? What does it mean in terms of this equation for $(2,8,-162)$ to be on this line?
– amd
May 19 '17 at 1:22
Managed to figure it out getting P equal to (5,-10,87). Thanks.
– John
May 19 '17 at 1:31
What is an equation of the tangent line at $r(t)$? What does it mean in terms of this equation for $(2,8,-162)$ to be on this line?
– amd
May 19 '17 at 1:22
What is an equation of the tangent line at $r(t)$? What does it mean in terms of this equation for $(2,8,-162)$ to be on this line?
– amd
May 19 '17 at 1:22
Managed to figure it out getting P equal to (5,-10,87). Thanks.
– John
May 19 '17 at 1:31
Managed to figure it out getting P equal to (5,-10,87). Thanks.
– John
May 19 '17 at 1:31
add a comment |
2 Answers
2
active
oldest
votes
Once $vec{r'}=(-1,-2t,-2-9t^2)$ the tangent line is given by $$vec t=lambdavec{r'}text{, }lambda in Bbb R$$
So, we can write
$$vec P+vec t=(2,8,-162)to\
(2-t,-1-t^2,-2t-3t^3)+(-lambda,-2lambda t,-2lambda-9lambda t^2)=(2,8,-162)$$
which means:
$$2-t-lambda=2to t=-lambda$$
$$-1-t^2-2lambda t=8$$
$$-2t-3t^3-9lambda t^2=-162$$
Can you finish?
@John: Is it clear?
– Arnaldo
May 22 '17 at 17:27
add a comment |
Let $vec{r}(t) = langle 2−t,−1−t^2,−2t−3t^3rangle$, where $tin mathbb{R}$. Then $vec{r}'(t) = langle -1, -2t, -2 -9t^2rangle$.
For any $t_0$ in the domain, a parametric equation of the tangent line at $t_0$ is given by
$$
vec{T}(t) = t :vec{r}'(t_0) + vec{r}(t_0), mbox{ where } tin mathbb{R}.
$$
Now, we want to find an equation of the tangent line when it is passing through $(2,8, -162)$.
Thus, setting the following equal to each other,
begin{align*}
tlangle -1, -2t, -2 -9t^2rangle + langle 2−t_0,−1−t_0^2,−2t_0−3t_0^3rangle = langle 2,8, -162 rangle,
end{align*}
we need to solve for $t_0$.
The above vector equation gives us three equations:
begin{align*}
-t+2-t_0&=2, hspace{4mm} (dagger) \
-2t_0t-1-t_0^2&=8, hspace{4mm} (ddagger) \
-2t-9t_0^2t-2t_0-3t_0^3&=-162. hspace{4mm} (Omega)\
end{align*}
Use the first equation $(dagger)$ to solve for $t:$
$$
t=-t_0.
$$
Let's substitute this into the second equation $(ddagger)$:
$$
2t_0^2 -1-t_0^2 = 8,
$$
which gives us $t_0^2 = 9$.
So $t_0 = pm 3$ while $t=mp 3$.
If $t_0=3$, then $t=-3$. We substitute these into the third equation $(Omega)$ to obtain:
$$
6+9cdot 9cdot 3 -2(3)-3(27) = 9(27)-3(27)=6(27) not= -162.
$$
We conclude that $t_0=-3$ while $t=3$, which we can check using the third equation $(Omega)$:
$$
-6-9cdot 9cdot 3 +2(3)+3(27) = -9(27)+3(27)=-6(27) = -162.
$$
So $P$ has position vector $vec{r}(-3)=langle 5,-10,87 rangle $, which is when its tangent line passes through the point $(2,8,−162)$.
add a comment |
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2 Answers
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2 Answers
2
active
oldest
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votes
Once $vec{r'}=(-1,-2t,-2-9t^2)$ the tangent line is given by $$vec t=lambdavec{r'}text{, }lambda in Bbb R$$
So, we can write
$$vec P+vec t=(2,8,-162)to\
(2-t,-1-t^2,-2t-3t^3)+(-lambda,-2lambda t,-2lambda-9lambda t^2)=(2,8,-162)$$
which means:
$$2-t-lambda=2to t=-lambda$$
$$-1-t^2-2lambda t=8$$
$$-2t-3t^3-9lambda t^2=-162$$
Can you finish?
@John: Is it clear?
– Arnaldo
May 22 '17 at 17:27
add a comment |
Once $vec{r'}=(-1,-2t,-2-9t^2)$ the tangent line is given by $$vec t=lambdavec{r'}text{, }lambda in Bbb R$$
So, we can write
$$vec P+vec t=(2,8,-162)to\
(2-t,-1-t^2,-2t-3t^3)+(-lambda,-2lambda t,-2lambda-9lambda t^2)=(2,8,-162)$$
which means:
$$2-t-lambda=2to t=-lambda$$
$$-1-t^2-2lambda t=8$$
$$-2t-3t^3-9lambda t^2=-162$$
Can you finish?
@John: Is it clear?
– Arnaldo
May 22 '17 at 17:27
add a comment |
Once $vec{r'}=(-1,-2t,-2-9t^2)$ the tangent line is given by $$vec t=lambdavec{r'}text{, }lambda in Bbb R$$
So, we can write
$$vec P+vec t=(2,8,-162)to\
(2-t,-1-t^2,-2t-3t^3)+(-lambda,-2lambda t,-2lambda-9lambda t^2)=(2,8,-162)$$
which means:
$$2-t-lambda=2to t=-lambda$$
$$-1-t^2-2lambda t=8$$
$$-2t-3t^3-9lambda t^2=-162$$
Can you finish?
Once $vec{r'}=(-1,-2t,-2-9t^2)$ the tangent line is given by $$vec t=lambdavec{r'}text{, }lambda in Bbb R$$
So, we can write
$$vec P+vec t=(2,8,-162)to\
(2-t,-1-t^2,-2t-3t^3)+(-lambda,-2lambda t,-2lambda-9lambda t^2)=(2,8,-162)$$
which means:
$$2-t-lambda=2to t=-lambda$$
$$-1-t^2-2lambda t=8$$
$$-2t-3t^3-9lambda t^2=-162$$
Can you finish?
answered May 19 '17 at 1:34
ArnaldoArnaldo
18.1k42246
18.1k42246
@John: Is it clear?
– Arnaldo
May 22 '17 at 17:27
add a comment |
@John: Is it clear?
– Arnaldo
May 22 '17 at 17:27
@John: Is it clear?
– Arnaldo
May 22 '17 at 17:27
@John: Is it clear?
– Arnaldo
May 22 '17 at 17:27
add a comment |
Let $vec{r}(t) = langle 2−t,−1−t^2,−2t−3t^3rangle$, where $tin mathbb{R}$. Then $vec{r}'(t) = langle -1, -2t, -2 -9t^2rangle$.
For any $t_0$ in the domain, a parametric equation of the tangent line at $t_0$ is given by
$$
vec{T}(t) = t :vec{r}'(t_0) + vec{r}(t_0), mbox{ where } tin mathbb{R}.
$$
Now, we want to find an equation of the tangent line when it is passing through $(2,8, -162)$.
Thus, setting the following equal to each other,
begin{align*}
tlangle -1, -2t, -2 -9t^2rangle + langle 2−t_0,−1−t_0^2,−2t_0−3t_0^3rangle = langle 2,8, -162 rangle,
end{align*}
we need to solve for $t_0$.
The above vector equation gives us three equations:
begin{align*}
-t+2-t_0&=2, hspace{4mm} (dagger) \
-2t_0t-1-t_0^2&=8, hspace{4mm} (ddagger) \
-2t-9t_0^2t-2t_0-3t_0^3&=-162. hspace{4mm} (Omega)\
end{align*}
Use the first equation $(dagger)$ to solve for $t:$
$$
t=-t_0.
$$
Let's substitute this into the second equation $(ddagger)$:
$$
2t_0^2 -1-t_0^2 = 8,
$$
which gives us $t_0^2 = 9$.
So $t_0 = pm 3$ while $t=mp 3$.
If $t_0=3$, then $t=-3$. We substitute these into the third equation $(Omega)$ to obtain:
$$
6+9cdot 9cdot 3 -2(3)-3(27) = 9(27)-3(27)=6(27) not= -162.
$$
We conclude that $t_0=-3$ while $t=3$, which we can check using the third equation $(Omega)$:
$$
-6-9cdot 9cdot 3 +2(3)+3(27) = -9(27)+3(27)=-6(27) = -162.
$$
So $P$ has position vector $vec{r}(-3)=langle 5,-10,87 rangle $, which is when its tangent line passes through the point $(2,8,−162)$.
add a comment |
Let $vec{r}(t) = langle 2−t,−1−t^2,−2t−3t^3rangle$, where $tin mathbb{R}$. Then $vec{r}'(t) = langle -1, -2t, -2 -9t^2rangle$.
For any $t_0$ in the domain, a parametric equation of the tangent line at $t_0$ is given by
$$
vec{T}(t) = t :vec{r}'(t_0) + vec{r}(t_0), mbox{ where } tin mathbb{R}.
$$
Now, we want to find an equation of the tangent line when it is passing through $(2,8, -162)$.
Thus, setting the following equal to each other,
begin{align*}
tlangle -1, -2t, -2 -9t^2rangle + langle 2−t_0,−1−t_0^2,−2t_0−3t_0^3rangle = langle 2,8, -162 rangle,
end{align*}
we need to solve for $t_0$.
The above vector equation gives us three equations:
begin{align*}
-t+2-t_0&=2, hspace{4mm} (dagger) \
-2t_0t-1-t_0^2&=8, hspace{4mm} (ddagger) \
-2t-9t_0^2t-2t_0-3t_0^3&=-162. hspace{4mm} (Omega)\
end{align*}
Use the first equation $(dagger)$ to solve for $t:$
$$
t=-t_0.
$$
Let's substitute this into the second equation $(ddagger)$:
$$
2t_0^2 -1-t_0^2 = 8,
$$
which gives us $t_0^2 = 9$.
So $t_0 = pm 3$ while $t=mp 3$.
If $t_0=3$, then $t=-3$. We substitute these into the third equation $(Omega)$ to obtain:
$$
6+9cdot 9cdot 3 -2(3)-3(27) = 9(27)-3(27)=6(27) not= -162.
$$
We conclude that $t_0=-3$ while $t=3$, which we can check using the third equation $(Omega)$:
$$
-6-9cdot 9cdot 3 +2(3)+3(27) = -9(27)+3(27)=-6(27) = -162.
$$
So $P$ has position vector $vec{r}(-3)=langle 5,-10,87 rangle $, which is when its tangent line passes through the point $(2,8,−162)$.
add a comment |
Let $vec{r}(t) = langle 2−t,−1−t^2,−2t−3t^3rangle$, where $tin mathbb{R}$. Then $vec{r}'(t) = langle -1, -2t, -2 -9t^2rangle$.
For any $t_0$ in the domain, a parametric equation of the tangent line at $t_0$ is given by
$$
vec{T}(t) = t :vec{r}'(t_0) + vec{r}(t_0), mbox{ where } tin mathbb{R}.
$$
Now, we want to find an equation of the tangent line when it is passing through $(2,8, -162)$.
Thus, setting the following equal to each other,
begin{align*}
tlangle -1, -2t, -2 -9t^2rangle + langle 2−t_0,−1−t_0^2,−2t_0−3t_0^3rangle = langle 2,8, -162 rangle,
end{align*}
we need to solve for $t_0$.
The above vector equation gives us three equations:
begin{align*}
-t+2-t_0&=2, hspace{4mm} (dagger) \
-2t_0t-1-t_0^2&=8, hspace{4mm} (ddagger) \
-2t-9t_0^2t-2t_0-3t_0^3&=-162. hspace{4mm} (Omega)\
end{align*}
Use the first equation $(dagger)$ to solve for $t:$
$$
t=-t_0.
$$
Let's substitute this into the second equation $(ddagger)$:
$$
2t_0^2 -1-t_0^2 = 8,
$$
which gives us $t_0^2 = 9$.
So $t_0 = pm 3$ while $t=mp 3$.
If $t_0=3$, then $t=-3$. We substitute these into the third equation $(Omega)$ to obtain:
$$
6+9cdot 9cdot 3 -2(3)-3(27) = 9(27)-3(27)=6(27) not= -162.
$$
We conclude that $t_0=-3$ while $t=3$, which we can check using the third equation $(Omega)$:
$$
-6-9cdot 9cdot 3 +2(3)+3(27) = -9(27)+3(27)=-6(27) = -162.
$$
So $P$ has position vector $vec{r}(-3)=langle 5,-10,87 rangle $, which is when its tangent line passes through the point $(2,8,−162)$.
Let $vec{r}(t) = langle 2−t,−1−t^2,−2t−3t^3rangle$, where $tin mathbb{R}$. Then $vec{r}'(t) = langle -1, -2t, -2 -9t^2rangle$.
For any $t_0$ in the domain, a parametric equation of the tangent line at $t_0$ is given by
$$
vec{T}(t) = t :vec{r}'(t_0) + vec{r}(t_0), mbox{ where } tin mathbb{R}.
$$
Now, we want to find an equation of the tangent line when it is passing through $(2,8, -162)$.
Thus, setting the following equal to each other,
begin{align*}
tlangle -1, -2t, -2 -9t^2rangle + langle 2−t_0,−1−t_0^2,−2t_0−3t_0^3rangle = langle 2,8, -162 rangle,
end{align*}
we need to solve for $t_0$.
The above vector equation gives us three equations:
begin{align*}
-t+2-t_0&=2, hspace{4mm} (dagger) \
-2t_0t-1-t_0^2&=8, hspace{4mm} (ddagger) \
-2t-9t_0^2t-2t_0-3t_0^3&=-162. hspace{4mm} (Omega)\
end{align*}
Use the first equation $(dagger)$ to solve for $t:$
$$
t=-t_0.
$$
Let's substitute this into the second equation $(ddagger)$:
$$
2t_0^2 -1-t_0^2 = 8,
$$
which gives us $t_0^2 = 9$.
So $t_0 = pm 3$ while $t=mp 3$.
If $t_0=3$, then $t=-3$. We substitute these into the third equation $(Omega)$ to obtain:
$$
6+9cdot 9cdot 3 -2(3)-3(27) = 9(27)-3(27)=6(27) not= -162.
$$
We conclude that $t_0=-3$ while $t=3$, which we can check using the third equation $(Omega)$:
$$
-6-9cdot 9cdot 3 +2(3)+3(27) = -9(27)+3(27)=-6(27) = -162.
$$
So $P$ has position vector $vec{r}(-3)=langle 5,-10,87 rangle $, which is when its tangent line passes through the point $(2,8,−162)$.
answered May 19 '17 at 1:49
Mee Seong ImMee Seong Im
2,7701517
2,7701517
add a comment |
add a comment |
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What is an equation of the tangent line at $r(t)$? What does it mean in terms of this equation for $(2,8,-162)$ to be on this line?
– amd
May 19 '17 at 1:22
Managed to figure it out getting P equal to (5,-10,87). Thanks.
– John
May 19 '17 at 1:31