Math Problem Statement

Solve the inverse function of(f of *)

Given the function f(x) = arccos(2x + 1) and g(x) = (x + 0.5) / (2x + 2), find the inverse function of f ∘ g.

Solution

Let's first break down the problem step-by-step to find the inverse of fgf \circ g based on the provided information.

Functions given:

  • f(x)=arccos(2x+1)f(x) = \arccos(2x + 1)
  • g(x)=x+0.52x+2g(x) = \frac{x + 0.5}{2x + 2}

We need to:

  1. Find the expression for fg(x)f \circ g(x), which means applying g(x)g(x) first and then applying f(x)f(x) to the result of g(x)g(x).

  2. Once we have fg(x)f \circ g(x), we'll determine the inverse of this composite function, (fg)1(x)(f \circ g)^{-1}(x).

Step 1: Compute fg(x)f \circ g(x)

The composite function fg(x)f \circ g(x) is defined as: (fg)(x)=f(g(x))(f \circ g)(x) = f(g(x))

Substituting g(x)=x+0.52x+2g(x) = \frac{x + 0.5}{2x + 2} into f(x)=arccos(2x+1)f(x) = \arccos(2x + 1):

f(g(x))=arccos(2(x+0.52x+2)+1)f(g(x)) = \arccos\left( 2 \left( \frac{x + 0.5}{2x + 2} \right) + 1 \right)

We simplify the expression inside the arccos\arccos: 2x+0.52x+2=2(x+0.5)2x+2=2x+12x+22 \cdot \frac{x + 0.5}{2x + 2} = \frac{2(x + 0.5)}{2x + 2} = \frac{2x + 1}{2x + 2}

So, we now have: f(g(x))=arccos(2x+12x+2+1)f(g(x)) = \arccos\left( \frac{2x + 1}{2x + 2} + 1 \right) Now, simplify the sum: f(g(x))=arccos(2x+1+2x+22x+2)=arccos(4x+32x+2)f(g(x)) = \arccos\left( \frac{2x + 1 + 2x + 2}{2x + 2} \right) = \arccos\left( \frac{4x + 3}{2x + 2} \right)

Thus, the expression for fg(x)f \circ g(x) is: fg(x)=arccos(4x+32x+2)f \circ g(x) = \arccos\left( \frac{4x + 3}{2x + 2} \right)

Step 2: Find the inverse (fg)1(x)(f \circ g)^{-1}(x)

To find the inverse, we set y=fg(x)y = f \circ g(x) and solve for xx in terms of yy.

y=arccos(4x+32x+2)y = \arccos\left( \frac{4x + 3}{2x + 2} \right) Apply cos\cos to both sides to eliminate the arccos\arccos: cos(y)=4x+32x+2\cos(y) = \frac{4x + 3}{2x + 2}

Now, solve this equation for xx: cos(y)(2x+2)=4x+3\cos(y)(2x + 2) = 4x + 3 2xcos(y)+2cos(y)=4x+32x\cos(y) + 2\cos(y) = 4x + 3 Move all terms involving xx to one side: 2xcos(y)4x=32cos(y)2x\cos(y) - 4x = 3 - 2\cos(y) Factor out xx: x(2cos(y)4)=32cos(y)x(2\cos(y) - 4) = 3 - 2\cos(y) Solve for xx: x=32cos(y)2cos(y)4x = \frac{3 - 2\cos(y)}{2\cos(y) - 4}

Thus, the inverse function of fg(x)f \circ g(x) is: (fg)1(x)=32cos(x)2cos(x)4(f \circ g)^{-1}(x) = \frac{3 - 2\cos(x)}{2\cos(x) - 4}

Summary:

The inverse of the function fgf \circ g is given by: (fg)1(x)=32cos(x)2cos(x)4(f \circ g)^{-1}(x) = \frac{3 - 2\cos(x)}{2\cos(x) - 4}

Would you like more details on the steps, or do you have any further questions? Here are five related questions for further exploration:

  1. How do we find the domain of the function fg(x)f \circ g(x)?
  2. What are the specific domain restrictions for f(x)=arccos(2x+1)f(x) = \arccos(2x + 1)?
  3. How does the derivative of fg(x)f \circ g(x) behave? Is it increasing or decreasing?
  4. Can fg(x)f \circ g(x) be expressed as a simpler function using trigonometric identities?
  5. What are the conditions under which the inverse function exists for fgf \circ g?

Tip: When working with composite functions, always apply the inner function first before proceeding with any other operations to avoid mistakes.

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Math Problem Analysis

Mathematical Concepts

Composite Functions
Inverse Functions
Trigonometry

Formulas

f(g(x)) = arccos((4x + 3) / (2x + 2))
(f ∘ g)^{-1}(x) = (3 - 2cos(x)) / (2cos(x) - 4)

Theorems

Inverse Function Theorem
Properties of Arccos Function

Suitable Grade Level

University Level