Calculus 2 : Parametric Calculations

Study concepts, example questions & explanations for Calculus 2

varsity tutors app store varsity tutors android store

Example Questions

Example Question #143 : Parametric

Given \(\displaystyle x=7t+9\) and \(\displaystyle y=t-1\), what is the length of the arc from \(\displaystyle 0\leq t\leq1\)?

Possible Answers:

\(\displaystyle 2\sqrt{2}\)

\(\displaystyle 7\sqrt{2}\)

\(\displaystyle 6\sqrt{2}\)

\(\displaystyle 4\sqrt{2}\)

\(\displaystyle 5\sqrt{2}\)

Correct answer:

\(\displaystyle 5\sqrt{2}\)

Explanation:

In order to find the arc length, we must use the arc length formula for parametric curves:

\(\displaystyle L=\int_{a}^{b}\sqrt{\left(\frac{dx}{dt}\right)^{2}+\left(\frac{dy}{dt}\right)^{2}}dt\).

Given  \(\displaystyle x=7t+9\) and \(\displaystyle y=t-1\), we can use using the Power Rule

 for all , to derive 

\(\displaystyle \frac{dx}{dt}=(1)7t^{1-1}+(0)9=7\) and \(\displaystyle \frac{dy}{dt}=(1)t^{1-1}-(0)1=1\).

Plugging these values and our boundary values for \(\displaystyle t\) into the arc length equation, we get:

\(\displaystyle L=\int_{0}^{1}\sqrt{(7)^{2}+(1)^{2}}dt\)

\(\displaystyle L=\int_{0}^{1}(\sqrt{49+1})dt\)

\(\displaystyle L=\int_{0}^{1}(\sqrt{50})dt\)

\(\displaystyle L=\int_{0}^{1}(\sqrt{25\times2})dt\)

\(\displaystyle L=\int_{0}^{1}(5\sqrt{2})dt\)

Now, using the Power Rule for Integrals \(\displaystyle \int x^{n}dx=\frac{x^{n+1}}{n+1}\) for all \(\displaystyle n\neq0\), we can determine that:

\(\displaystyle L=(5t\sqrt{2})_{0}^{1}\textrm{}\)

\(\displaystyle L=5(1)\sqrt{2}-5(0)\sqrt{2}\)

\(\displaystyle L=5\sqrt{2}\)

 

Example Question #144 : Parametric

Given \(\displaystyle x=5t+2\) and \(\displaystyle y=7t+10\), what is the arc length between \(\displaystyle 0\leqt\leq t\leq2\)?

Possible Answers:

\(\displaystyle 7\sqrt{74}\)

\(\displaystyle 2\sqrt{74}\)

\(\displaystyle 5\sqrt{74}\)

\(\displaystyle 3\sqrt{74}\)

\(\displaystyle \sqrt{74}\)

Correct answer:

\(\displaystyle 2\sqrt{74}\)

Explanation:

In order to find the arc length, we must use the arc length formula for parametric curves:

\(\displaystyle L=\int_{a}^{b}\sqrt{\left(\frac{dx}{dt}\right)^{2}+\left(\frac{dy}{dt}\right)^{2}}dt\).

Given  \(\displaystyle x=5t+2\) and \(\displaystyle y=7t+10\),we can use using the Power Rule
for all , to derive

\(\displaystyle \frac{dx}{dt}=(1)5t^{1-1}+(0)2=5\) and 

\(\displaystyle \frac{dy}{dt}=(1)7t^{1-1}+(0)10=7\) .

Plugging these values and our boundary values for into the arc length equation, we get:

\(\displaystyle L=\int_{0}^{2}\sqrt{(5)^{2}+(7)^{2}}dt\)

\(\displaystyle L=\int_{0}^{2}(\sqrt{25+49})dt\)

\(\displaystyle L=\int_{0}^{2}(\sqrt{74})dt\)

Now, using the Power Rule for Integrals

for all ,

we can determine that:

\(\displaystyle L=[t\sqrt{74}]_{0}^{2}\textrm{}dt\)

\(\displaystyle L=2\sqrt{74}-0\sqrt{74}\)

\(\displaystyle L=2\sqrt{74}\)

Example Question #145 : Parametric

Given \(\displaystyle x=6t-4\) and \(\displaystyle y=4t+6\), what is the arc length between \(\displaystyle 0\leqt\leq t\leq3\)?

Possible Answers:

\(\displaystyle 5\sqrt{13}\)

\(\displaystyle 8\sqrt{13}\)

\(\displaystyle 4\sqrt{13}\)

\(\displaystyle 7\sqrt{13}\)

\(\displaystyle 6\sqrt{13}\)

Correct answer:

\(\displaystyle 6\sqrt{13}\)

Explanation:

In order to find the arc length, we must use the arc length formula for parametric curves:

\(\displaystyle L=\int_{a}^{b}\sqrt{\left(\frac{dx}{dt}\right)^{2}+\left(\frac{dy}{dt}\right)^{2}}dt\).

Given  \(\displaystyle x=6t-4\) and \(\displaystyle y=4t+6\), we can use using the Power Rule

 for all , to derive 

\(\displaystyle \frac{dx}{dt}=(1)6t^{1-1}-(0)4=6\) and 

\(\displaystyle \frac{dy}{dt}=(1)4t^{1-1}+(0)6=4\).

Plugging these values and our boundary values for  into the arc length equation, we get:

\(\displaystyle L=\int_{0}^{3}\sqrt{(6)^{2}+(4)^{2}}dt\)

\(\displaystyle L=\int_{0}^{3}(\sqrt{36+16})dt\)

\(\displaystyle L=\int_{0}^{3}(\sqrt{52})dt\)

\(\displaystyle L=\int_{0}^{3}(\sqrt{13\times4})dt\)

\(\displaystyle L=\int_{0}^{3}(2\sqrt{13})dt\)

Now, using the Power Rule for Integrals

 for all ,

we can determine that:

\(\displaystyle L=[2t\sqrt{13}]_{0}^{3}\textrm{}dt\)

\(\displaystyle L=2(3)\sqrt{13}-2(0)\sqrt{13}\)

\(\displaystyle L=6\sqrt{13}\)

Example Question #1 : Parametric Form

Given \(\displaystyle x=t+10\) and \(\displaystyle y=2t-9\), what is the arc length between \(\displaystyle 0\leqt\leq t\leq4\)?

Possible Answers:

\(\displaystyle 3\sqrt{5}\)

\(\displaystyle \sqrt{5}\)

\(\displaystyle 4\sqrt{5}\)

\(\displaystyle 5\sqrt{5}\)

\(\displaystyle 2\sqrt{5}\)

Correct answer:

\(\displaystyle 4\sqrt{5}\)

Explanation:

In order to find the arc length, we must use the arc length formula for parametric curves:

\(\displaystyle L=\int_{a}^{b}\sqrt{\left(\frac{dx}{dt}\right)^{2}+\left(\frac{dy}{dt}\right)^{2}}dt\).

Given  \(\displaystyle x=t+10\) and \(\displaystyle y=2t-9\), we can use using the Power Rule

 for all , to derive 

\(\displaystyle \frac{dx}{dt}=(1)t^{1-1}+(0)10=1\) and 

\(\displaystyle \frac{dy}{dt}=(1)2t^{1-1}-(0)9=2\).

Plugging these values and our boundary values for  into the arc length equation, we get:

\(\displaystyle L=\int_{0}^{4}\sqrt{(1)^{2}+(2)^{2}}dt\)

\(\displaystyle L=\int_{0}^{4}(\sqrt{1+4})dt\)

\(\displaystyle L=\int_{0}^{4}(\sqrt{5})dt\)

Now, using the Power Rule for Integrals

 for all ,

we can determine that:

\(\displaystyle L=[t\sqrt{5}]_{0}^{4}\textrm{}dt\)

\(\displaystyle L=(4)\sqrt{5}-(0)\sqrt{5}\)

\(\displaystyle L=4\sqrt{5}\)

Example Question #4 : Parametric, Polar, And Vector Functions

Given \(\displaystyle x=4t-5\) and \(\displaystyle y=6t+2\), what is the length of the arc from \(\displaystyle 0\leq t\leq2\)?

Possible Answers:

\(\displaystyle 3\sqrt{13}\)

\(\displaystyle 6\sqrt{13}\)

\(\displaystyle 4\sqrt{13}\)

\(\displaystyle 5\sqrt{13}\)

\(\displaystyle 7\sqrt{13}\)

Correct answer:

\(\displaystyle 4\sqrt{13}\)

Explanation:

In order to find the arc length, we must use the arc length formula for parametric curves:

\(\displaystyle L=\int_{a}^{b}\sqrt{\left(\frac{dx}{dt}\right)^{2}+\left(\frac{dy}{dt}\right)^{2}}dt\).

Given \(\displaystyle x=4t-5\) and \(\displaystyle y=6t+2\), we can use using the Power Rule

for all  , to derive

\(\displaystyle \frac{dx}{dt}=(1)4t^{1-1}-(0)5=4\) and

\(\displaystyle \frac{dy}{dt}=(1)6t^{1-1}+(0)2=6\) .

Plugging these values and our boundary values for into the arc length equation, we get:

\(\displaystyle L=\int_{0}^{2}(\sqrt{(4)^{2}+(6)^{2}}dt\)

\(\displaystyle L=\int_{0}^{2}(\sqrt{16+36})dt\)

\(\displaystyle L=\int_{0}^{2}(\sqrt{52})dt\)

\(\displaystyle L=\int_{0}^{2}(\sqrt{4\times13})dt\)

\(\displaystyle L=\int_{0}^{2}(2\sqrt{13})dt\)

Now, using the Power Rule for Integrals

for all ,

we can determine that:

\(\displaystyle L=[2t\sqrt{13}]_{0}^{2}\textrm{}\)

\(\displaystyle L=2(2)\sqrt{13}-2(0)\sqrt{13}\)

\(\displaystyle L=4\sqrt{13}\)

Example Question #151 : Parametric

Given \(\displaystyle x=9t+4\) and \(\displaystyle y=4t-1\), what is the length of the arc from \(\displaystyle 0\leq t\leq3\)?

Possible Answers:

\(\displaystyle 7\sqrt{97}\)

\(\displaystyle 4\sqrt{97}\)

\(\displaystyle 6\sqrt{97}\)

\(\displaystyle 5\sqrt{97}\)

\(\displaystyle 3\sqrt{97}\)

Correct answer:

\(\displaystyle 3\sqrt{97}\)

Explanation:

In order to find the arc length, we must use the arc length formula for parametric curves:

\(\displaystyle L=\int_{a}^{b}\sqrt{\left(\frac{dx}{dt}\right)^{2}+\left(\frac{dy}{dt}\right)^{2}}dt\).

Given \(\displaystyle x=9t+4\) and \(\displaystyle y=4t-1\), we can use using the Power Rule

 for all , to derive 

\(\displaystyle \frac{dx}{dt}=(1)9t^{1-1}+(0)4=9\) and 

\(\displaystyle \frac{dy}{dt}=(1)4t^{1-1}-(0)1=4\).

Plugging these values and our boundary values for  into the arc length equation, we get:

\(\displaystyle L=\int_{0}^{3}(\sqrt{(9)^{2}+(4)^{2}}dt\)

\(\displaystyle L=\int_{0}^{3}(\sqrt{81+16})dt\)

\(\displaystyle L=\int_{0}^{3}(\sqrt{97})dt\)

Now, using the Power Rule for Integrals

 for all ,

we can determine that:

\(\displaystyle L=[t\sqrt{97}]_{0}^{3}\textrm{}\)

\(\displaystyle L=(3)\sqrt{97}-(0)\sqrt{97}\)

\(\displaystyle L=3\sqrt{97}\)

Example Question #151 : Parametric

Given \(\displaystyle x=t-11\) and \(\displaystyle y=7t+6\), what is the length of the arc from \(\displaystyle 0\leq t\leq4\)?

Possible Answers:

\(\displaystyle 35\sqrt{2}\)

\(\displaystyle 15\sqrt{2}\)

\(\displaystyle 30\sqrt{2}\)

\(\displaystyle 25\sqrt{2}\)

\(\displaystyle 20\sqrt{2}\)

Correct answer:

\(\displaystyle 20\sqrt{2}\)

Explanation:

In order to find the arc length, we must use the arc length formula for parametric curves:

\(\displaystyle L=\int_{a}^{b}\sqrt{\left(\frac{dx}{dt}\right)^{2}+\left(\frac{dy}{dt}\right)^{2}}dt\).

Given \(\displaystyle x=t-11\) and \(\displaystyle y=7t+6\), we can use using the Power Rule

 for all , to derive 

\(\displaystyle \frac{dx}{dt}=(1)t^{1-1}-(0)11=1\)  and 

\(\displaystyle \frac{dy}{dt}=(1)7t^{1-1}+(0)6=7\).

Plugging these values and our boundary values for  into the arc length equation, we get:

\(\displaystyle L=\int_{0}^{4}(\sqrt{(1)^{2}+(7)^{2}}dt\)

\(\displaystyle L=\int_{0}^{4}(\sqrt{1+49})dt\)

\(\displaystyle L=\int_{0}^{4}(\sqrt{50})dt\)

\(\displaystyle L=\int_{0}^{4}(\sqrt{25\times2})dt\)

\(\displaystyle L=\int_{0}^{4}(5\sqrt{2})dt\)

Now, using the Power Rule for Integrals

 for all ,

we can determine that:

\(\displaystyle L=[5t\sqrt{2}]_{0}^{4}\textrm{}\)

\(\displaystyle L=5(4)\sqrt{2}-5(0)\sqrt{2}\)

\(\displaystyle L=20\sqrt{2}\)

 

Example Question #152 : Parametric

Eliminate the parameter \(\displaystyle t\) from \(\displaystyle x=t^{3}+3t^{2}-3t-12\) and \(\displaystyle y=t-8\) to write this system as one equation.

Possible Answers:

\(\displaystyle x=3y^{2}+6y-3\)

\(\displaystyle x=3y^{2}\)

\(\displaystyle x=6y^{2}+6y-3\)

\(\displaystyle x=\frac{y^{2}+6y-3}{3y^{2}}\)

\(\displaystyle x=(y+8)^{3}+3(y+8)^{2}-3(y+8)-12\)

Correct answer:

\(\displaystyle x=(y+8)^{3}+3(y+8)^{2}-3(y+8)-12\)

Explanation:

 

To eliminate the parameter \(\displaystyle t\) from \(\displaystyle x\) and \(\displaystyle y\), we will solve the \(\displaystyle y\) equation for \(\displaystyle t\) and substitute the new expression into the \(\displaystyle x\) equation. We could also solve the \(\displaystyle x\) equation for \(\displaystyle t\) and substitute the new expression into the \(\displaystyle y\) equation, depending on which is easier.

For our equations, \(\displaystyle x=t^{3}+3t^{2}-3t-12\) and \(\displaystyle y=t-8\), it is easiest to solve the \(\displaystyle y\) equation for \(\displaystyle t\), giving us \(\displaystyle t=y+8\).  

Substituting our new expression for \(\displaystyle t\) into the \(\displaystyle x\) equation, we get

\(\displaystyle x=(y+8)^{3}+3(y+8)^{2}-3(y+8)-12\)

Example Question #13 : Parametric Calculations

Eliminate the parameter \(\displaystyle t\) from \(\displaystyle x=ln(t)\) and \(\displaystyle y=ln(4t)\) to write this system as one equation.

Possible Answers:

\(\displaystyle y=ln(t)\)

\(\displaystyle x=ln(\frac{1}{4})+y\)

\(\displaystyle x=ln(4y)\)

\(\displaystyle x=y\)

\(\displaystyle x=e^{y}\)

Correct answer:

\(\displaystyle x=ln(\frac{1}{4})+y\)

Explanation:

To eliminate the parameter \(\displaystyle t\) from \(\displaystyle x\) and \(\displaystyle y\), we will solve the \(\displaystyle y\) equation for \(\displaystyle t\) and substitute the new expression into the \(\displaystyle x\) equation. We could also solve the \(\displaystyle x\) equation for \(\displaystyle t\) and substitute the new expression into the \(\displaystyle y\) equation, depending on which is easier. 

For our equations,  \(\displaystyle x=ln(t)\) and \(\displaystyle y=ln(4t)\) , we will rearrange the \(\displaystyle y\) equation

\(\displaystyle y=ln(4t)\)

To eleiminate the \(\displaystyle ln\) on the right side of the equation, we will take the exponential of both sides of the equation

\(\displaystyle e^{y}=e^{ln(4t)}\)

Using the exponential identity \(\displaystyle e^{ln(x)}=x\)

\(\displaystyle e^{y}=4t\)

\(\displaystyle \frac{1}{4}e^{y}=t\)

Substituting this value of \(\displaystyle t\) into the \(\displaystyle x\) equation, we have

\(\displaystyle x=ln(\frac{1}{4}e^{y})\)

Using the logarithmic identity, \(\displaystyle ln(xy)=ln(x)+ln(y)\)

\(\displaystyle ln(\frac{1}{4}e^{y})=ln(\frac{1}{4})+ln(e^{y})\)

The using the identity, \(\displaystyle ln(e^{x})=x\)

\(\displaystyle ln(\frac{1}{4})+ln(e^{y})=ln(\frac{1}{4})+y\)

Giving us the final expression

\(\displaystyle x=ln(\frac{1}{4})+y\)

Example Question #11 : Parametric Calculations

Eliminate the parameter \(\displaystyle t\) from \(\displaystyle x=e^{2t}\) and \(\displaystyle y=e^{5t}\).

 

Possible Answers:

\(\displaystyle y=e^{10x}\)

\(\displaystyle y=t\)

\(\displaystyle y=x^{2.5}\)

\(\displaystyle y=x\)

\(\displaystyle y=x^{10}\)

 

Correct answer:

\(\displaystyle y=x^{10}\)

 

Explanation:

To eliminate the parameter \(\displaystyle t\) from \(\displaystyle x\) and \(\displaystyle y\), we will solve the \(\displaystyle y\) equation for \(\displaystyle t\) and substitute the new expression into the \(\displaystyle x\) equation. We could also solve the \(\displaystyle x\) equation for \(\displaystyle t\) and substitute the new expression into the \(\displaystyle y\) equation, depending on which is easier. 

For our equations, \(\displaystyle x=e^{2t}\) and \(\displaystyle y=e^{5t}\), we will rearrange the \(\displaystyle x\) equation.

\(\displaystyle x=e^{2t}\)

To eliminate the exponential from the right side of the equation, we will take the \(\displaystyle ln\) of both sides of the equation.

\(\displaystyle ln(x)=ln(e^{2t})\)

Using the logarithmic identity, \(\displaystyle ln(e^{x})=x\)

\(\displaystyle ln(x)=2t\)

\(\displaystyle \frac{1}{2}ln(x)=t\)

Substituting this value of \(\displaystyle t\) into the \(\displaystyle y\) equation, we have

\(\displaystyle y=e^{5*\frac{1}{2}ln(x)}=e^{10ln(x)}\)

Using the logarithmic identity \(\displaystyle cln(x)=ln(x^{c})\), where \(\displaystyle c\) is a constant

\(\displaystyle e^{10ln(x)}=e^{ln(x^{10})}=x^{10}\)

Therefore \(\displaystyle y=x^{10}\).

Learning Tools by Varsity Tutors