# Changes

## Calculus:Error log

, 6 July
no edit summary
{| class="sortable" border="1"
! Page !! Error description !! Version where it was introduced !! Version where it was corrected !! Why error? Why not caught? ("I" refers to [[User:Vipul|Vipul]])
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| [[Logistic function]] || The derivative expression in the "Key data" table had an extra minus sign. The derivative in the section that actually computed it was correct || || [https://calculus.subwiki.org/w/index.php?title=Logistic_function&oldid=3172 July 6, 2019] ||
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| [[Second derivative test for a function of multiple variables]] || wrote that the derivative must be $(-1)^r$, where the intended statement was that the sign of the derivative must be $(-1)^r$ || || [http://calculus.subwiki.org/w/index.php?title=Second_derivative_test_for_a_function_of_multiple_variables&oldid=3121 July 4, 2015] || carelessness
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| [[Limit]] || In a discussion of the relation between one-sided and two-sided limits, forgot an "and are equal" (not in the main definition, but in an aside) || || [http://calculus.subwiki.org/w/index.php?title=Limit&oldid=3116 May 16, 2015]|| carelessness, insufficient review
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| [[Derivative of differentiable function satisfies intermediate value property]] || at one stage in an explanation, used two-sided derivative notation where only one-sided derivatives are guaranteed to exist. || || [http://calculus.subwiki.org/w/index.php?title=Derivative_of_differentiable_function_satisfies_intermediate_value_property&oldid=2284 January 20, 2013] || minor issue
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| [[inverse function theorem]] || omitted a continuity condition/constraint || || [http://calculus.subwiki.org/w/index.php?title=Inverse_function_theorem&oldid=2281 January 20, 2013] || genuine conceptual misunderstanding; didn't think through proof clearly and didn't rack brains for counterexample.
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| [[first derivative test]] || omitted continuity from "succinct version" (now "short version") of test; it was included in the lengthier description || || [http://calculus.subwiki.org/w/index.php?title=First_derivative_test&direction=next&oldid=1420 May 3, 2012] || error in judgment, not so much in fact (because continuity assumption was stated in the longer version)
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| [[second derivative test]] || Didn't state that the point of concern must be a critical point in the "What the test states" section though it was stated in the "What the test is for" section || [http://calculus.subwiki.org/w/index.php?title=Second_derivative_test&oldid=328 September 19, 2011] || [http://calculus.subwiki.org/w/index.php?title=Second_derivative_test&oldid=1381 May 2, 2012] || didn't review, revisit page
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| [[point of local extremum implies critical point]] || Fact numbers in the Explanation column for the local minimum case were somewhat messed up (although fact numbers in the Facts used column were correct), also used "maximum" instead of "minimum" at a couple of places in the "Given data used" column || [http://calculus.subwiki.org/w/index.php?title=Point_of_local_extremum_implies_critical_point&oldid=509 October 20, 2011] || [http://calculus.subwiki.org/w/index.php?title=Point_of_local_extremum_implies_critical_point&oldid=1374 April 25, 2012] and [http://calculus.subwiki.org/w/index.php?title=Point_of_local_extremum_implies_critical_point&oldid=1532 May 4, 2012] || copy-paste error from maximum to minimum. I should really have caught the second error at the time I caught the first ... it just goes to show that one has to be doubly, triply careful when reading tabular proofs and check that all columns are correct and up to date.
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| [[first derivative test]] || had "right" in place of "left" for one of the case rows || [http://calculus.subwiki.org/w/index.php?title=First_derivative_test&oldid=311 September 19, 2011] || [http://calculus.subwiki.org/w/index.php?title=First_derivative_test&oldid=1331 April 24, 2012] || didn't review, revisit page
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| [[product rule for partial differentiation]] || directional derivative instead of gradient at one place, and a bunch of minor typos, missing open parenthesis, use of $\cdot$ for function product at one place (might confuse with dot product), and extraneous statements like "let $\overline{u}$ be a unit vector" in definition components where no unit vector was needed. || || [http://calculus.subwiki.org/w/index.php?title=Product_rule_for_partial_differentiation&oldid=1059 April 2, 2012] || didn't revisit page often enough
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| [[partial derivative]] || Had "x" in place of "y" in one of the derivative descriptions/definitions. || [http://calculus.subwiki.org/w/index.php?title=Partial_derivative&direction=prev&oldid=721 December 17, 2011] || [http://calculus.subwiki.org/w/index.php?title=Partial_derivative&oldid=1009 April 1, 2012] || Didn't revisit page often enough
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