ii. Let f: A → B and g: B → C be invertible mappings; that is, mappings such that f-¹ and g-¹ exist. Show that (gof)-¹ = f-¹g-¹.

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### Invertible Mappings and Their Compositions

**Problem Statement:**

Let \( f: A \rightarrow B \) and \( g: B \rightarrow C \) be invertible mappings; that is, mappings such that \( f^{-1} \) and \( g^{-1} \) exist. Show that:

\[ (g \circ f)^{-1} = f^{-1} \circ g^{-1} \]

### Explanation:

1. **Definitions:**
   - \( f \) is a function that maps elements from set \( A \) to set \( B \).
   - \( g \) is a function that maps elements from set \( B \) to set \( C \).
   - Both \( f \) and \( g \) are invertible, meaning they have corresponding inverse functions \( f^{-1} \) and \( g^{-1} \), respectively.

2. **Goal:**
   - We need to show that the inverse of the composition \( g \circ f \) is equal to the composition of the inverses in the reverse order.

### Proof Outline:

1. Consider any element \( c \) in set \( C \). First, we apply \( g^{-1} \) to map \( c \) back to an element \( b \) in set \( B \):

   \[ b = g^{-1}(c) \]

2. Next, apply \( f^{-1} \) to map \( b \) back to an element \( a \) in set \( A \):

   \[ a = f^{-1}(b) = f^{-1}(g^{-1}(c)) \]

3. Therefore, for an element \( c \) in \( C \):

   \[ a = (f^{-1} \circ g^{-1})(c) \]

4. By definition of inverses and composition of functions, \( (g \circ f)(a) \) should map \( a \) back to \( c \):

   \[ (g \circ f)(a) = c \]

5. As a result:

   \[ (g \circ f)^{-1}(c) = (f^{-1} \circ g^{-1})(c) \]

Thus, we have shown that \( (g \circ f)^{-1} = f^{-1} \circ g^{-1} \).
Transcribed Image Text:### Invertible Mappings and Their Compositions **Problem Statement:** Let \( f: A \rightarrow B \) and \( g: B \rightarrow C \) be invertible mappings; that is, mappings such that \( f^{-1} \) and \( g^{-1} \) exist. Show that: \[ (g \circ f)^{-1} = f^{-1} \circ g^{-1} \] ### Explanation: 1. **Definitions:** - \( f \) is a function that maps elements from set \( A \) to set \( B \). - \( g \) is a function that maps elements from set \( B \) to set \( C \). - Both \( f \) and \( g \) are invertible, meaning they have corresponding inverse functions \( f^{-1} \) and \( g^{-1} \), respectively. 2. **Goal:** - We need to show that the inverse of the composition \( g \circ f \) is equal to the composition of the inverses in the reverse order. ### Proof Outline: 1. Consider any element \( c \) in set \( C \). First, we apply \( g^{-1} \) to map \( c \) back to an element \( b \) in set \( B \): \[ b = g^{-1}(c) \] 2. Next, apply \( f^{-1} \) to map \( b \) back to an element \( a \) in set \( A \): \[ a = f^{-1}(b) = f^{-1}(g^{-1}(c)) \] 3. Therefore, for an element \( c \) in \( C \): \[ a = (f^{-1} \circ g^{-1})(c) \] 4. By definition of inverses and composition of functions, \( (g \circ f)(a) \) should map \( a \) back to \( c \): \[ (g \circ f)(a) = c \] 5. As a result: \[ (g \circ f)^{-1}(c) = (f^{-1} \circ g^{-1})(c) \] Thus, we have shown that \( (g \circ f)^{-1} = f^{-1} \circ g^{-1} \).
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