Verify the identity.

Trigonometry (11th Edition)
11th Edition
ISBN:9780134217437
Author:Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Publisher:Margaret L. Lial, John Hornsby, David I. Schneider, Callie Daniels
Chapter1: Trigonometric Functions
Section: Chapter Questions
Problem 1RE: 1. Give the measures of the complement and the supplement of an angle measuring 35°.
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**Verification of the Identity:**

\[
\frac{\cos(u) \sec(u)}{\tan(u)} = \cot(u)
\]

**Objective:** Use a Reciprocal Identity to rewrite the expression and then simplify.

Step-by-Step Solution:

1. Begin with the given expression:

\[
\frac{\cos(u) \sec(u)}{\tan(u)}
\]

2. Apply the Reciprocal Identity. Expand \(\tan(u)\) as \(\frac{\sin(u)}{\cos(u)}\):

\[
\frac{\cos(u) \sec(u)}{\frac{\sin(u)}{\cos(u)}}
\]

Red note with an "X" indicates an incorrect approach by rewriting the expression as \((\cos(u) \sec(u))(\tan(u))\). This approach is not correct.

3. Simplify the multiplication:

\[
= \cos(u) \cdot \sec(u) \cdot \frac{\cos(u)}{\sin(u)}
\]

4. Recognize that \(\sec(u) = \frac{1}{\cos(u)}\):

\[
= \cos(u) \cdot \frac{1}{\cos(u)} \cdot \frac{\cos(u)}{\sin(u)}
\]

5. Simplify the intermediate expression:

\[
= \cos(u) \cdot \frac{1}{\cos(u)} \cdot \frac{\cos(u)}{\sin(u)}
\]

So, 

\[
= \cos(u) \cdot \frac{\cos(u)}{\cos(u)} \cdot \frac{1}{\sin(u)}
\]

6. Simplify \(\frac{\cos(u)}{\cos(u)}\) to 1:

\[
= 1 \cdot \frac{1}{\sin(u)}
\]

7. Thus, the expression simplifies to the cotangent function:

\[
= \cot(u) \quad \checkmark
\]
Transcribed Image Text:**Verification of the Identity:** \[ \frac{\cos(u) \sec(u)}{\tan(u)} = \cot(u) \] **Objective:** Use a Reciprocal Identity to rewrite the expression and then simplify. Step-by-Step Solution: 1. Begin with the given expression: \[ \frac{\cos(u) \sec(u)}{\tan(u)} \] 2. Apply the Reciprocal Identity. Expand \(\tan(u)\) as \(\frac{\sin(u)}{\cos(u)}\): \[ \frac{\cos(u) \sec(u)}{\frac{\sin(u)}{\cos(u)}} \] Red note with an "X" indicates an incorrect approach by rewriting the expression as \((\cos(u) \sec(u))(\tan(u))\). This approach is not correct. 3. Simplify the multiplication: \[ = \cos(u) \cdot \sec(u) \cdot \frac{\cos(u)}{\sin(u)} \] 4. Recognize that \(\sec(u) = \frac{1}{\cos(u)}\): \[ = \cos(u) \cdot \frac{1}{\cos(u)} \cdot \frac{\cos(u)}{\sin(u)} \] 5. Simplify the intermediate expression: \[ = \cos(u) \cdot \frac{1}{\cos(u)} \cdot \frac{\cos(u)}{\sin(u)} \] So, \[ = \cos(u) \cdot \frac{\cos(u)}{\cos(u)} \cdot \frac{1}{\sin(u)} \] 6. Simplify \(\frac{\cos(u)}{\cos(u)}\) to 1: \[ = 1 \cdot \frac{1}{\sin(u)} \] 7. Thus, the expression simplifies to the cotangent function: \[ = \cot(u) \quad \checkmark \]
# Verifying Trigonometric Identities

## Verifying the Identity:
Given the identity:

\[ \frac{\sec(t) - \cos(t)}{\sec(t)} = \sin^2(t) \]

We aim to verify this identity using fundamental trigonometric identities.

## Step-by-Step Verification

### Step 1: Use a Reciprocal Identity
Firstly, we use the reciprocal identity for \(\sec(t)\):

\[ \sec(t) = \frac{1}{\cos(t)} \]

Rewrite the given expression in terms of cosine only:

\[ \frac{\sec(t) - \cos(t)}{\sec(t)} \]

Substitute the reciprocal identity \(\sec(t) = \frac{1}{\cos(t)}\):

\[ \frac{\frac{1}{\cos(t)} - \cos(t)}{\frac{1}{\cos(t)}} \]

### Step 2: Simplify the Expression
Factor out \(\frac{1}{\cos(t)}\):

\[ \left( \frac{1}{\cos(t)} \right) \left( \frac{1}{\cos(t)} - \cos(t) \right) \]

Combine the terms in the numerator:

\[ \frac{1}{\cos(t)} \left( \frac{1 - \cos^2(t)}{\cos(t)} \right) \]

Multiply out:

\[ = \frac{1 - \cos^2(t)}{\cos^2(t)} \]

### Step 3: Use a Pythagorean Identity
Recall the Pythagorean identity:

\[ \sin^2(t) + \cos^2(t) = 1 \]

So,

\[ 1 - \cos^2(t) = \sin^2(t) \]

Substitute \(\sin^2(t)\) into the expression:

\[ \frac{\sin^2(t)}{\cos^2(t)} \]

### Step 4: Simplify Further
Recognize that:

\[ \frac{\sin^2(t)}{\cos^2(t)} = \tan^2(t) \]

Since the given expression simplifies to \( \sin^2(t) \), the identity is verified:

\[ \boxed{\sin^2(t)} \]

By carefully substituting identities and simplifying step-by-step, we verify that:

\[ \frac{\sec(t) - \cos(t)}{\sec(t)}
Transcribed Image Text:# Verifying Trigonometric Identities ## Verifying the Identity: Given the identity: \[ \frac{\sec(t) - \cos(t)}{\sec(t)} = \sin^2(t) \] We aim to verify this identity using fundamental trigonometric identities. ## Step-by-Step Verification ### Step 1: Use a Reciprocal Identity Firstly, we use the reciprocal identity for \(\sec(t)\): \[ \sec(t) = \frac{1}{\cos(t)} \] Rewrite the given expression in terms of cosine only: \[ \frac{\sec(t) - \cos(t)}{\sec(t)} \] Substitute the reciprocal identity \(\sec(t) = \frac{1}{\cos(t)}\): \[ \frac{\frac{1}{\cos(t)} - \cos(t)}{\frac{1}{\cos(t)}} \] ### Step 2: Simplify the Expression Factor out \(\frac{1}{\cos(t)}\): \[ \left( \frac{1}{\cos(t)} \right) \left( \frac{1}{\cos(t)} - \cos(t) \right) \] Combine the terms in the numerator: \[ \frac{1}{\cos(t)} \left( \frac{1 - \cos^2(t)}{\cos(t)} \right) \] Multiply out: \[ = \frac{1 - \cos^2(t)}{\cos^2(t)} \] ### Step 3: Use a Pythagorean Identity Recall the Pythagorean identity: \[ \sin^2(t) + \cos^2(t) = 1 \] So, \[ 1 - \cos^2(t) = \sin^2(t) \] Substitute \(\sin^2(t)\) into the expression: \[ \frac{\sin^2(t)}{\cos^2(t)} \] ### Step 4: Simplify Further Recognize that: \[ \frac{\sin^2(t)}{\cos^2(t)} = \tan^2(t) \] Since the given expression simplifies to \( \sin^2(t) \), the identity is verified: \[ \boxed{\sin^2(t)} \] By carefully substituting identities and simplifying step-by-step, we verify that: \[ \frac{\sec(t) - \cos(t)}{\sec(t)}
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