@@ -290,37 +290,43 @@ def arc_area(self):
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&\hspace{1em}- \left( \sum_{j=0}^n P_j^{(1)} b_{j,n} \right)
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\left( n \sum_{k=0}^{n-1} (P_{k+1}^{(0)} -
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P_{k}^{(0)}) b_{j,n} \right)
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- dt
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+ dt,
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- Where :math:`b_{\nu, n}(t) = {n \choose \nu} t^\nu {(1 - t)}^{n-\nu}`
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+ where :math:`b_{\nu, n}(t) = {n \choose \nu} t^\nu {(1 - t)}^{n-\nu}`
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is the :math:`\nu`'th Bernstein polynomial of degree :math:`n`.
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Grouping :math:`t^l(1-t)^m` terms together for each :math:`l`,
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:math:`m`, we get that the integrand becomes
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.. math::
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- & \sum_{j=0}^n \sum_{k=0}^{n-1}
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+ \sum_{j=0}^n \sum_{k=0}^{n-1}
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{n \choose j} {{n - 1} \choose k}
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- [P_j^{(0)} (P_{k+1}^{(1)} - P_{k}^{(1)})
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- - P_j^{(1)} (P_{k+1}^{(0)} - P_{k}^{(0)})]
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- t^{j + k} {(1 - t)}^{2n - 1 - j - k}
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- \\
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- &= \sum_{j=0}^n \sum_{k=0}^{n-1}
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+ &\left[P_j^{(0)} (P_{k+1}^{(1)} - P_{k}^{(1)})
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+ - P_j^{(1)} (P_{k+1}^{(0)} - P_{k}^{(0)})\right] \\
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+ &\hspace{1em}\times{}t^{j + k} {(1 - t)}^{2n - 1 - j - k}
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+
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+ or just
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+
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+ .. math::
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+
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+ \sum_{j=0}^n \sum_{k=0}^{n-1}
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\frac{{n \choose j} {{n - 1} \choose k}}
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{{{2n - 1} \choose {j+k}}}
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[P_j^{(0)} (P_{k+1}^{(1)} - P_{k}^{(1)})
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- P_j^{(1)} (P_{k+1}^{(0)} - P_{k}^{(0)})]
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- b_{j+k,2n-1}(t)
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+ b_{j+k,2n-1}(t).
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Interchanging sum and integral, and using the fact that :math:`\int_0^1
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b_{\nu, n}(t) dt = \frac{1}{n + 1}`, we conclude that the
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- original integral (:math:`\frac{1}{2}\int_0^1 B(t) \cdot n(t) dt`) can
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+ original integral can
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simply be written as
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.. math::
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- \frac{1}{4}\sum_{j=0}^n \sum_{k=0}^{n-1}
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+ \frac{1}{2}&\int_0^1 B(t) \cdot n(t) dt
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+ \\
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+ &= \frac{1}{4}\sum_{j=0}^n \sum_{k=0}^{n-1}
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\frac{{n \choose j} {{n - 1} \choose k}}
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{{{2n - 1} \choose {j+k}}}
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[P_j^{(0)} (P_{k+1}^{(1)} - P_{k}^{(1)})
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