Drawn from $\,P\,$ the tangent vectors $\,\mr_u’(P)\,,\,\mr_v’(P)\,$ and $\mr_w’(P)\,$ span a parallel-epipedon. Determine the volume of this parallel-epipedon. Possibly illustrate using Maple.
hint
The volume can be found as the absolute value of the determinant of the matrix that has the spanning vectors as columns.
answer
Volume = 3.
B
Determine the Jacobi function corresponding to $\,\mr\,$.
hint
The Jacobi function in a spatial integral is the absolute value of a determinant of a matrix. what are the elements of the matrix? And what was it we actually found in the last question?
answer
$\jac r{u,v,w}=u^2+2v^2.$
C
Determine the volume of $\Omega\,$.
hint
The volume of $\Omega$ can be computed as the integral of the function 1 - and do not forget Jacobi.
answer
$32.$
Exercise 3: The Unit Sphere
In the $\,(x,z)$-plane in space the profile curve $\,C\,$ is given by
Determine a parametric representation for the surface $\mathcal S$ that appears by rotating $C\,$, viewed as a space curve, $\,2\pi\,$ about the $\,z$-axis.
hint
See formula line (25-30) in eNote 25.
B
Explain that every point $\,(x,y,z)\,$ on $\,\mathcal S\,$ fulfills the equation $\,x^2+y^2+z^2=1\,,$ and that $\,\mathcal S\,$ is the unit sphere with centre at the origin.
C
Determine the area of $\,\mathcal S\,$.
answer
The area is computed as $\,\int_{\mathcal S} 1\, d\mu=4\pi\,.$
A profile field $\,M\,$ in the $\,(x,z)$-plane in space is given by the parametric representation
State a parametric representation K for the solid of revolution that appears when $\,M\,$ is rotated the angle $\,2\pi\,$ about the $\,z$-axis. Which geometrical object are we talking about?
in the $\,(x,y)$-plane. we consider the spatial field $\,B\,$ between $\,A\,$ and the graph for $\,h\,$.
Find a parametric representation for $\,B\,$. Plot using the parametric representation the part of the graph for $h$ determined by B. Then determine the corresponding Jacobi function, and determine
$$\int_{B} x^2-y\,d\mu\,.$$
hint
It is most obvious to use $\mr(u,v,w)=(u,v,w\cdot h(u,v)\,)\,.$ Find yourself the intervals for the three parameters.
answer
$$\int_{B} x^2-y\,d\mu=-\frac{68}{15}\,.$$
A region $\,C\,$ in the $\,(x,y)$-plane appears by shifting in parallel the unit circular disc
$$\,\left\{(x,y)\,|\,x^2+y^2\leq1\,\right\}\,$$
that lies in the first quadrant by the vector $\,(1,0)\,.$ We consider the spatial region $\,D\,$ between $\,C\,$ and the graph for $\,h\,$.
B
Find a parametric representation for $\,D\,$. Plot using the parametric representation the part of the graph for $\,h\,$ determined by $\,D\,$. Then determine the corresponding Jacobi function and the volume $\,D\,.$
hint
First you shall need a parametrization of $\,C,$ which you then can insert into
$$\,(x,y,z)=(x,y,h(x,y)\,)\,.$$
answer
$$\Vol D=1+\frac{5}{16}\,\pi\,.$$
Exercise 5: Surface of Revolution. Parametrization and Integration
In the $\,(x,z)$-plane in space is given the filled triangle T that has the vertices
State a parametric representation for the surface of revolution $\,\Omega\,$ that appears when T is rotated the angle $\,2\pi\,$ about the $\,z$-axis. Which geometrical object are we talking about?