2/pi*x\
sin |----|
\ l /
sin((pi*x)/l)^2
Let .
Apply the power rule: goes to
Then, apply the chain rule. Multiply by :
Let .
The derivative of sine is cosine:
Then, apply the chain rule. Multiply by :
The derivative of a constant times a function is the constant times the derivative of the function.
The derivative of a constant times a function is the constant times the derivative of the function.
Apply the power rule: goes to
So, the result is:
So, the result is:
The result of the chain rule is:
The result of the chain rule is:
Now simplify:
The answer is:
/pi*x\ /pi*x\
2*pi*cos|----|*sin|----|
\ l / \ l /
------------------------
l
2 / 2/pi*x\ 2/pi*x\\
2*pi *|cos |----| - sin |----||
\ \ l / \ l //
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2
l