Korean CSAT Mathematics common mistakes
Korean CSAT Mathematics · Understand the traps and how to avoid them.
Ignoring a forbidden denominator
Multiplication can hide a value for which the original expression is undefined.
What to do instead
Record excluded values first and substitute final candidates.
Using n rather than n minus one for a term
The first term already occurs at index one before any common differences are added.
What to do instead
Write a small sequence and verify the term formula against its first entries.
Calling every zero derivative a maximum
A stationary point can be a minimum or neither kind of extremum.
What to do instead
Compare neighboring derivative signs or relevant function values.
Dropping the integration constant
Different functions can have the same derivative but different initial values.
What to do instead
Use the supplied initial condition after integrating.
Adding vector magnitudes instead of vectors
Different directions can cancel or reinforce components rather than produce a simple sum of lengths.
What to do instead
Add components first, then calculate the resulting magnitude.
Choosing only the first trigonometric angle
A periodic function can attain the same value at several allowed inputs.
What to do instead
List candidate angles and filter them by the supplied interval.
Averaging group means equally
Groups of different sizes contribute different numbers of observations to the combined total.
What to do instead
Recover total scores and divide by total group size.
Treating consecutive draws as unchanged without replacement
The first draw changes the composition of the remaining population.
What to do instead
Recalculate the second conditional probability using the remaining objects.