Supremum
About points...
We associate a certain number of points with each exercise.
When you click an exercise into a collection, this number will be taken as points for the exercise, kind of "by default".
But once the exercise is on the collection, you can edit the number of points for the exercise in the collection independently, without any effect on "points by default" as represented by the number here.
That being said... How many "default points" should you associate with an exercise upon creation?
As with difficulty, there is no straight forward and generally accepted way.
But as a guideline, we tend to give as many points by default as there are mathematical steps to do in the exercise.
Again, very vague... But the number should kind of represent the "work" required.
When you click an exercise into a collection, this number will be taken as points for the exercise, kind of "by default".
But once the exercise is on the collection, you can edit the number of points for the exercise in the collection independently, without any effect on "points by default" as represented by the number here.
That being said... How many "default points" should you associate with an exercise upon creation?
As with difficulty, there is no straight forward and generally accepted way.
But as a guideline, we tend to give as many points by default as there are mathematical steps to do in the exercise.
Again, very vague... But the number should kind of represent the "work" required.
About difficulty...
We associate a certain difficulty with each exercise.
When you click an exercise into a collection, this number will be taken as difficulty for the exercise, kind of "by default".
But once the exercise is on the collection, you can edit its difficulty in the collection independently, without any effect on the "difficulty by default" here.
Why we use chess pieces? Well... we like chess, we like playing around with \(\LaTeX\)-fonts, we wanted symbols that need less space than six stars in a table-column... But in your layouts, you are of course free to indicate the difficulty of the exercise the way you want.
That being said... How "difficult" is an exercise? It depends on many factors, like what was being taught etc.
In physics exercises, we try to follow this pattern:
Level 1 - One formula (one you would find in a reference book) is enough to solve the exercise. Example exercise
Level 2 - Two formulas are needed, it's possible to compute an "in-between" solution, i.e. no algebraic equation needed. Example exercise
Level 3 - "Chain-computations" like on level 2, but 3+ calculations. Still, no equations, i.e. you are not forced to solve it in an algebraic manner. Example exercise
Level 4 - Exercise needs to be solved by algebraic equations, not possible to calculate numerical "in-between" results. Example exercise
Level 5 -
Level 6 -
When you click an exercise into a collection, this number will be taken as difficulty for the exercise, kind of "by default".
But once the exercise is on the collection, you can edit its difficulty in the collection independently, without any effect on the "difficulty by default" here.
Why we use chess pieces? Well... we like chess, we like playing around with \(\LaTeX\)-fonts, we wanted symbols that need less space than six stars in a table-column... But in your layouts, you are of course free to indicate the difficulty of the exercise the way you want.
That being said... How "difficult" is an exercise? It depends on many factors, like what was being taught etc.
In physics exercises, we try to follow this pattern:
Level 1 - One formula (one you would find in a reference book) is enough to solve the exercise. Example exercise
Level 2 - Two formulas are needed, it's possible to compute an "in-between" solution, i.e. no algebraic equation needed. Example exercise
Level 3 - "Chain-computations" like on level 2, but 3+ calculations. Still, no equations, i.e. you are not forced to solve it in an algebraic manner. Example exercise
Level 4 - Exercise needs to be solved by algebraic equations, not possible to calculate numerical "in-between" results. Example exercise
Level 5 -
Level 6 -
Question
Solution
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Exercise:
Bestimme das Supremum von fxyx-y über * E leftxy:x^+y^le right. *
Solution:
Der Gradient der Funktion fxyx-y ist nabla fxy leftarrayc-arrayright &neq Da der Gradient nirgs verschwindet kann das Maximum nicht im Innern der Ellipse x^+y^ angenommen werden. Es muss also auf der Ellipse liegen. Mit Lagrange finden wir gxy;lambda fxy + lambdax^+y^ nabla gxy;lambda x^+y^ labellagrange. Die zweite dieser drei Gleichungen liefert nabla gxy;lambda leftarrayc-arrayright + lambda leftarraycxyarrayright &mustbe was auf lambda x - Rightarrow x-fraclambdaquadmboxbzw. labelxygl lambda y Rightarrow yfraclambdalabelxygl führt. Setzt man diese Ergebnisse nun in Gleichung reflagrange ein so kommt man auf x^+y^ fraclambda^leftfrac+fracright fraclambda^frac lambda pm sqrtfrac Setzt man das nun zurück ein also bei Gleichungen refxygl bzw. refxygl so gibt das x mp fracsqrtfrac y pm fracsqrtfrac. Das Maximum der Funktion x-y auf der Ellipse ist somit x-y sqrtfrac leftmpfrac mpfracright mp frac sqrtfrac was fracsqrt ergibt.
Bestimme das Supremum von fxyx-y über * E leftxy:x^+y^le right. *
Solution:
Der Gradient der Funktion fxyx-y ist nabla fxy leftarrayc-arrayright &neq Da der Gradient nirgs verschwindet kann das Maximum nicht im Innern der Ellipse x^+y^ angenommen werden. Es muss also auf der Ellipse liegen. Mit Lagrange finden wir gxy;lambda fxy + lambdax^+y^ nabla gxy;lambda x^+y^ labellagrange. Die zweite dieser drei Gleichungen liefert nabla gxy;lambda leftarrayc-arrayright + lambda leftarraycxyarrayright &mustbe was auf lambda x - Rightarrow x-fraclambdaquadmboxbzw. labelxygl lambda y Rightarrow yfraclambdalabelxygl führt. Setzt man diese Ergebnisse nun in Gleichung reflagrange ein so kommt man auf x^+y^ fraclambda^leftfrac+fracright fraclambda^frac lambda pm sqrtfrac Setzt man das nun zurück ein also bei Gleichungen refxygl bzw. refxygl so gibt das x mp fracsqrtfrac y pm fracsqrtfrac. Das Maximum der Funktion x-y auf der Ellipse ist somit x-y sqrtfrac leftmpfrac mpfracright mp frac sqrtfrac was fracsqrt ergibt.
Meta Information
Exercise:
Bestimme das Supremum von fxyx-y über * E leftxy:x^+y^le right. *
Solution:
Der Gradient der Funktion fxyx-y ist nabla fxy leftarrayc-arrayright &neq Da der Gradient nirgs verschwindet kann das Maximum nicht im Innern der Ellipse x^+y^ angenommen werden. Es muss also auf der Ellipse liegen. Mit Lagrange finden wir gxy;lambda fxy + lambdax^+y^ nabla gxy;lambda x^+y^ labellagrange. Die zweite dieser drei Gleichungen liefert nabla gxy;lambda leftarrayc-arrayright + lambda leftarraycxyarrayright &mustbe was auf lambda x - Rightarrow x-fraclambdaquadmboxbzw. labelxygl lambda y Rightarrow yfraclambdalabelxygl führt. Setzt man diese Ergebnisse nun in Gleichung reflagrange ein so kommt man auf x^+y^ fraclambda^leftfrac+fracright fraclambda^frac lambda pm sqrtfrac Setzt man das nun zurück ein also bei Gleichungen refxygl bzw. refxygl so gibt das x mp fracsqrtfrac y pm fracsqrtfrac. Das Maximum der Funktion x-y auf der Ellipse ist somit x-y sqrtfrac leftmpfrac mpfracright mp frac sqrtfrac was fracsqrt ergibt.
Bestimme das Supremum von fxyx-y über * E leftxy:x^+y^le right. *
Solution:
Der Gradient der Funktion fxyx-y ist nabla fxy leftarrayc-arrayright &neq Da der Gradient nirgs verschwindet kann das Maximum nicht im Innern der Ellipse x^+y^ angenommen werden. Es muss also auf der Ellipse liegen. Mit Lagrange finden wir gxy;lambda fxy + lambdax^+y^ nabla gxy;lambda x^+y^ labellagrange. Die zweite dieser drei Gleichungen liefert nabla gxy;lambda leftarrayc-arrayright + lambda leftarraycxyarrayright &mustbe was auf lambda x - Rightarrow x-fraclambdaquadmboxbzw. labelxygl lambda y Rightarrow yfraclambdalabelxygl führt. Setzt man diese Ergebnisse nun in Gleichung reflagrange ein so kommt man auf x^+y^ fraclambda^leftfrac+fracright fraclambda^frac lambda pm sqrtfrac Setzt man das nun zurück ein also bei Gleichungen refxygl bzw. refxygl so gibt das x mp fracsqrtfrac y pm fracsqrtfrac. Das Maximum der Funktion x-y auf der Ellipse ist somit x-y sqrtfrac leftmpfrac mpfracright mp frac sqrtfrac was fracsqrt ergibt.
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ETH 1. Vordiplom Analysis Frühling 1996 by TeXercises