JEE Advance - Mathematics (1983 - No. 50)
Explanation
The statement "The derivative of an even function is always an odd function" is Option A: TRUE.
To understand why this is true, let's first define even and odd functions:
An even function is a function $ f(x) $ that satisfies the condition:
$$ f(-x) = f(x) $$
An odd function is a function $ g(x) $ that satisfies the condition:
$$ g(-x) = -g(x) $$
Now, let's consider the derivative of an even function. Let $ f(x) $ be an even function, meaning:
$$ f(-x) = f(x) $$
We want to find the derivative $ f'(x) $ and determine if it is odd. Using the definition of the derivative, we have:
$$ f'(x) = \lim_{{h \to 0}} \frac{f(x+h) - f(x)}{h} $$
Since $ f(x) $ is even, we have:
$$ f(x) = f(-x) $$
Taking the derivative of both sides with respect to $ x $, we get:
$$ f'(-x) \cdot (-1) = f'(x) $$
or
$$ f'(-x) = -f'(x) $$
This shows that the derivative $ f'(x) $ satisfies the condition for being an odd function. Therefore, the derivative of an even function is indeed always an odd function.
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