autodiff: Test linear algebra

[EricCousineau-TRI]

@manuelli ran into these issue, and I hadn't actually tested these yet.

(There's a form of these in #8452, but I, uh, forgot to port them...)

xref:
#8116
numpy/numpy#11332

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This change is 

[EricCousineau-TRI]

+@soonho-tri for feature review, please.
+@sherm1 for platform review, please.

Reviewable status: all discussions resolved, platform LGTM missing

[soonho-tri]

BTW, do you plan to provide a link to this example in documentation (e.g. in another file)?

Reviewed 1 of 1 files at r1.
Reviewable status: 1 unresolved discussion, LGTM missing from assignee sherm1, platform LGTM from [soonho-tri] (waiting on @EricCousineau-TRI and @sherm1)

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bindings/pydrake/test/autodiffutils_test.py, line 199 at r1 (raw file):

        Bf = np.array([[2., 2]]).T
        C2 = np.dot(A, Bf)  # Leverages implicit casting.
        self._check_array(C, [[AD(4, [4., 2])]])

I guess you wanted to write:

self._check_array(C2, [[AD(4, [4., 0])]])

[sherm1]

Platform

Reviewed 1 of 1 files at r1.
Reviewable status: 1 unresolved discussion, platform LGTM from [soonho-tri, sherm1] (waiting on @EricCousineau-TRI)

[EricCousineau-TRI]

BTW, do you plan to provide a link to this example in documentation (e.g. in another file)?

Will think about how to do that in doc/python.rst...

Reviewable status: 1 unresolved discussion, platform LGTM from [soonho-tri, sherm1] (waiting on @sherm1 and @soonho-tri)

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bindings/pydrake/test/autodiffutils_test.py, line 199 at r1 (raw file):

Previously, soonho-tri (Soonho Kong) wrote…

I guess you wanted to write:

self._check_array(C2, [[AD(4, [4., 0])]])

Done. Thanks!

[soonho-tri]

Reviewed 1 of 1 files at r2.
Reviewable status: complete! all discussions resolved, platform LGTM from [soonho-tri, sherm1]