To find the derivative of the function \( f(x) = x \cdot \csc(x) \) using the first principle of derivatives, we will apply the definition of the derivative. The first principle states that the derivative of a function at a point is the limit of the average rate of change of the function as the interval approaches zero. Mathematically, this is expressed as:
f'(x) = lim (h → 0) [(f(x + h) - f(x)) / h]
Step-by-Step Derivation of f(x) = x * csc(x)
Let's break this down into manageable steps:
1. Define the Function
We start with:
f(x) = x \cdot \csc(x) = x / \sin(x)
2. Calculate f(x + h)
Next, we need to find \( f(x + h) \):
f(x + h) = (x + h) \cdot \csc(x + h) = (x + h) / \sin(x + h)
3. Set Up the Difference Quotient
Now, we can substitute these into the limit definition:
f'(x) = lim (h → 0) [((x + h) / \sin(x + h) - x / \sin(x)) / h]
4. Simplify the Expression
To simplify this, we need a common denominator:
= lim (h → 0) [( (x + h) \cdot \sin(x) - x \cdot \sin(x + h) ) / (h \cdot \sin(x) \cdot \sin(x + h))]
5. Expand and Simplify Further
Using the sine addition formula and properties of limits, we can further simplify the numerator:
= lim (h → 0) [(x \cdot \sin(x) + h \cdot \sin(x) - x \cdot (\sin(x) + h \cdot \cos(x))) / (h \cdot \sin(x) \cdot \sin(x + h))]
= lim (h → 0) [(h \cdot \sin(x) - h \cdot x \cdot \cos(x)) / (h \cdot \sin(x) \cdot \sin(x + h))]
6. Cancel h and Take the Limit
Now we can cancel \( h \) from the numerator and denominator:
= lim (h → 0) [( \sin(x) - x \cdot \cos(x)) / (\sin(x) \cdot \sin(x + h))]
As \( h \) approaches 0, \( \sin(x + h) \) approaches \( \sin(x) \), so we have:
= ( \sin(x) - x \cdot \cos(x)) / (\sin^2(x))
7. Final Result
Thus, the derivative of \( f(x) = x \cdot \csc(x) \) is:
f'(x) = \frac{\sin(x) - x \cdot \cos(x)}{\sin^2(x)}
Finding the Derivative of e^√x
Now, let's tackle the second part of your question regarding \( g(x) = e^{\sqrt{x}} \) using the first principle.
1. Define the Function
We start with:
g(x) = e^{\sqrt{x}}
2. Calculate g(x + h)
Next, we find \( g(x + h) \):
g(x + h) = e^{\sqrt{x + h}}
3. Set Up the Difference Quotient
Using the definition of the derivative:
g'(x) = lim (h → 0) [(e^{\sqrt{x + h}} - e^{\sqrt{x}}) / h]
4. Factor Out e^{√x}
We can factor out \( e^{\sqrt{x}} \):
= e^{\sqrt{x}} \cdot lim (h → 0) [(e^{\sqrt{x + h} - \sqrt{x}} - 1) / h]
5. Use the Exponential Limit
As \( h \) approaches 0, \( \sqrt{x + h} - \sqrt{x} \) can be approximated using the derivative of \( \sqrt{x} \):
= \frac{1}{2\sqrt{x}} \cdot h
Thus, we can rewrite the limit as:
= e^{\sqrt{x}} \cdot lim (h → 0) [(e^{\frac{1}{2\sqrt{x}} \cdot h} - 1) / h]
6. Evaluate the Limit
Using the fact that \( lim (u → 0) \frac{e^u - 1}{u} = 1 \), we find:
= e^{\sqrt{x}} \cdot \frac{1}{2\sqrt{x}}
7. Final Result
Therefore, the derivative of \( g(x) = e^{\sqrt{x}} \) is:
g'(x) = \frac{e^{\sqrt{x}}}{2\sqrt{x}}
In summary, both derivatives were calculated using the first principle, demonstrating the application of limits and algebraic manipulation. If you have further questions or need clarification on any