Test math extensions :math:`E = m c^2`
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 This is inline math: :math:`a^2 + b^2 = c^2`.
 
 .. math:: a^2 + b^2 = c^2
 
 .. math::
 
    a + 1 < b
 
 .. math::
    :label: foo
 
    e^{i\pi} = 1
 
 .. math::
    :label:
 
    e^{ix} = \cos x + i\sin x
 
 .. math::
 
    n \in \mathbb N
 
 .. math::
    :nowrap:
 
    a + 1 < b
 
 Referencing equation :eq:`foo`.