diff --git a/ptx/sec_curvature.ptx b/ptx/sec_curvature.ptx index df08b0ba1..ecebce505 100644 --- a/ptx/sec_curvature.ptx +++ b/ptx/sec_curvature.ptx @@ -208,7 +208,7 @@ We find it with \vec r(2) = \la 1/5, 18/5\ra.

-
+
Graphing \vec r in with parameters t and s @@ -687,7 +687,7 @@ Being able to think of curvature in terms of the radius of a circle is very useful.

-
+
Illustrating the osculating circles for the curve seen in @@ -757,7 +757,7 @@ .

-
+
Examining the curvature of y=x^2 @@ -834,26 +834,10 @@

-

- While this is not a particularly nice formula, - it does explicitly tell us what the curvature is at a given t value. - To maximize \kappa(t), - we should solve \kappa'(t)=0 for t. - This is doable, but very time consuming. - Instead, consider the graph of - \kappa(t) as given in . - We see that \kappa is maximized at two t values; - using a numerical solver, we find these values are t\approx\pm 0.189. - In we graph \vrt and indicate the points where curvature is maximized. -

- -
- Understanding the curvature of a curve in space - -
- The curvature of \vec{r}(t) +
+ The curvature of \vec{r}(t) in - + A plot of the curvature as a function of the parameter t.

@@ -885,11 +869,11 @@

-
- A plot of the curve \vec{r}(t)=\la t, t^2, 2t^3\ra +
+ A plot of the curve \vec{r}(t)=\la t, t^2, 2t^3\ra in - + A plot of the vector-valued function in this example, with points of maximum curvature marked.

@@ -950,9 +934,19 @@

- -
+

+ While this is not a particularly nice formula, + it does explicitly tell us what the curvature is at a given t value. + To maximize \kappa(t), + we should solve \kappa'(t)=0 for t. + This is doable, but very time consuming. + Instead, consider the graph of + \kappa(t) as given in . + We see that \kappa is maximized at two t values; + using a numerical solver, we find these values are t\approx\pm 0.189. + In we graph \vrt and indicate the points where curvature is maximized. +

diff --git a/ptx/sec_tan_norm.ptx b/ptx/sec_tan_norm.ptx index 098580294..1638ccfac 100644 --- a/ptx/sec_tan_norm.ptx +++ b/ptx/sec_tan_norm.ptx @@ -68,7 +68,7 @@ since they are only length 1.)

-
+
Plotting unit tangent vectors in @@ -382,7 +382,7 @@ These are sketched in .

-
+
Plotting unit tangent and normal vectors in @@ -447,17 +447,7 @@ - +

The previous example was once again @@ -517,7 +507,7 @@ we compute the unit tangent and normal vectors for t=-1,0 and 1 and sketch them in .

-
+
Plotting unit tangent and normal vectors in @@ -607,6 +597,18 @@

+ +

+ A brief consideration of this theorem may make one wonder: what if the graph of \vec r does + not have a concave side? What if \vec r is a line? +

+

+ This exposes a shortcoming in our definition of \unitnormal(t), where + we require that \unittangent(t) be smooth, i.e., that \unittangentprime(t) \neq \vec 0, + a requirement that lines do not fulfill. One may still want to compute a normal vector for a given line, though. + For straight lines in the x,y plane, it is most common to orient the normal vector 90^\circ + counterclockwise from the tangent vector. For lines in three dimensions, there is no preferred choice of normal vector. +

@@ -802,7 +804,7 @@ gives a graph of the path for reference.

-
+
Graphing \vec r(t) in @@ -875,7 +877,7 @@ which we plot in .

-
+
Plotting the position of a thrown ball, with 1s increments shown @@ -1043,10 +1045,7 @@

If \unittangent(t) is a unit tangent vector, - what is \norm{\unittangent(t)}? -

- -

+ what is \norm{\unittangent(t)}?

@@ -1072,10 +1071,7 @@

If \unitnormal(t) is a unit normal vector, - what is \unitnormal(t)\cdot \vrp(t)? -

- -

+ what is \unitnormal(t)\cdot \vrp(t)?

diff --git a/ptx/sec_vvf.ptx b/ptx/sec_vvf.ptx index 50ee1a456..a164a0d35 100644 --- a/ptx/sec_vvf.ptx +++ b/ptx/sec_vvf.ptx @@ -648,7 +648,7 @@ \vec r(t) = \vec p(t) + \vec c(t) = \la \cos(t) + t,-\sin(t) +1\ra, which is graphed in .

-
+
The cycloid in @@ -750,7 +750,7 @@ The displacement of \vec r(t) on [-1,1] is thus \vec d = \la 0,1\ra - \la 0,-1\ra = \la 0,2\ra.

-
+
Graphing the displacement of a position function in diff --git a/ptx/sec_vvf_calc.ptx b/ptx/sec_vvf_calc.ptx index e63c127f2..f69815f5f 100644 --- a/ptx/sec_vvf_calc.ptx +++ b/ptx/sec_vvf_calc.ptx @@ -19,7 +19,7 @@ The theorem following the definition shows that in practice, taking limits of vector-valued functions is no more difficult than taking limits of real-valued functions.

-