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   Die deutschen Artikel sind hier.

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   Comprehension of mathematics is improved mainly by doing and not just by reading about it. For this reason, many of these articles are structured in a manner that, for the best learning success, encourages to read the “Approach” section first, and then to try to do the derivation, as outlined therein, yourself. The “Derivation” section is highly detailed on purpose, so if you get stuck anywhere, it should be easily possible to look-up the next step.

     Calculus of Variations

• Derivation of the Euler-Lagrange equation via Gateaux differential
• Derivation of the fundamental lemma of the Calculus of Variations

     Derivatives

• Derivation of the derivative of f(x)=x via difference quotient
• Derivation of the derivative of f(x)=x^s via implicit differentiation
• Derivation of the derivative of the natural logarithm via implicit differentiation

     Other

• Derivation of Euler’s formula via differential equation
• Derivation of the quadratic formula by completing the square