CHAPTER IX.
INTRODUCING A USEFUL DODGE.
Sometimes one is stumped by finding that the expression to be differentiated is too complicated to tackle directly.
Thus, the equation
is awkward to a beginner.
Now the dodge to turn the difficulty is this: Write some symbol, such as , for the expression ; then the equation becomes
,
which you can easily manage; for
.
Then tackle the expression
,
and differentiate it with respect to ,
.