Math Problem Statement

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Problem

Let [g(x)=\dfrac{\cos(x)}{\sin(x)}].

Find [g'(x)].

Choose 1 answer:

Choose 1 answer:

(Choice A)   

[\dfrac{1}{\sin^2(x)}]

A

[\dfrac{1}{\sin^2(x)}]

(Choice B)   

[\dfrac{\sin^2(x)-\cos^2(x)}{\sin^2(x)}]

B

[\dfrac{\sin^2(x)-\cos^2(x)}{\sin^2(x)}]

(Choice C)   

[-\dfrac{1}{\sin^2(x)}]

C

[-\dfrac{1}{\sin^2(x)}]

(Choice D)   

[\dfrac{\cos^2(x)-\sin^2(x)}{\sin^2(x)}]

D

[\dfrac{\cos^2(x)-\sin^2(x)}{\sin^2(x)}]

Solution

To find the derivative g(x)g'(x) of the function g(x)=cos(x)sin(x)g(x) = \frac{\cos(x)}{\sin(x)}, we can use the quotient rule. Recall that the quotient rule is:

(u(x)v(x))=u(x)v(x)u(x)v(x)(v(x))2\left(\frac{u(x)}{v(x)}\right)' = \frac{u'(x)v(x) - u(x)v'(x)}{(v(x))^2}

For the function g(x)=cos(x)sin(x)g(x) = \frac{\cos(x)}{\sin(x)}, let:

  • u(x)=cos(x)u(x) = \cos(x)
  • v(x)=sin(x)v(x) = \sin(x)

Now, compute the derivatives:

  • u(x)=sin(x)u'(x) = -\sin(x)
  • v(x)=cos(x)v'(x) = \cos(x)

Applying the quotient rule:

g(x)=u(x)v(x)u(x)v(x)(v(x))2=(sin(x))sin(x)cos(x)cos(x)sin2(x)g'(x) = \frac{u'(x)v(x) - u(x)v'(x)}{(v(x))^2} = \frac{(-\sin(x))\sin(x) - \cos(x)\cos(x)}{\sin^2(x)}

Simplify the expression in the numerator:

g(x)=sin2(x)cos2(x)sin2(x)g'(x) = \frac{-\sin^2(x) - \cos^2(x)}{\sin^2(x)}

Using the Pythagorean identity sin2(x)+cos2(x)=1\sin^2(x) + \cos^2(x) = 1:

g(x)=(sin2(x)+cos2(x))sin2(x)=1sin2(x)g'(x) = \frac{-(\sin^2(x) + \cos^2(x))}{\sin^2(x)} = \frac{-1}{\sin^2(x)}

So the correct derivative is:

g(x)=1sin2(x)g'(x) = -\frac{1}{\sin^2(x)}

This corresponds to Choice C.

Would you like any further explanations?

Here are 5 related questions to explore this concept further:

  1. How would you find the second derivative g(x)g''(x) of this function?
  2. What is the derivative of g(x)=cot(x)g(x) = \cot(x), and how does it relate to this problem?
  3. Can you apply the chain rule to simplify g(x)g'(x) in a different form?
  4. How does the derivative g(x)g'(x) change at specific values, such as x=π4x = \frac{\pi}{4}?
  5. What happens to g(x)g(x) and g(x)g'(x) as xx approaches 0 or π\pi?

Tip: Remember that trigonometric identities, like the Pythagorean identity, can simplify your work when dealing with derivatives involving trigonometric functions.

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Math Problem Analysis

Mathematical Concepts

Differentiation
Trigonometric Functions
Quotient Rule

Formulas

Quotient rule for differentiation

Theorems

Pythagorean identity

Suitable Grade Level

Advanced High School