1+ cos 20 Show that cos 0
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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Verify using proofs
![**Trigonometric Identity Proof**
The image presents a trigonometric identity that needs to be proven:
\[ \cos^2 \theta = \frac{1 + \cos 2\theta}{2} \]
**Explanation:**
This identity relates the square of the cosine of an angle (\(\theta\)) to the cosine of twice that angle (\(2\theta\)). It is a commonly used identity in trigonometry known as the "Power-Reduction Formulas." These formulas are useful for simplifying expressions involving trigonometric functions to make integration or equation-solving more manageable.
**Proof Overview:**
To prove this identity, we can start by using the double-angle formula for cosine:
\[ \cos 2\theta = 2\cos^2 \theta - 1 \]
Rearrange the formula to express \(\cos^2 \theta\):
\[ 2\cos^2 \theta = 1 + \cos 2\theta \]
Now, divide both sides by 2:
\[ \cos^2 \theta = \frac{1 + \cos 2\theta}{2} \]
This completes the proof, verifying the identity as shown in the equation.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F4167b07b-ab2c-42e3-ab89-9f12261de975%2Fdc7fe700-b93c-4b3d-a1ba-b5a2b0c03e2f%2F1vqxvpc_processed.png&w=3840&q=75)
Transcribed Image Text:**Trigonometric Identity Proof**
The image presents a trigonometric identity that needs to be proven:
\[ \cos^2 \theta = \frac{1 + \cos 2\theta}{2} \]
**Explanation:**
This identity relates the square of the cosine of an angle (\(\theta\)) to the cosine of twice that angle (\(2\theta\)). It is a commonly used identity in trigonometry known as the "Power-Reduction Formulas." These formulas are useful for simplifying expressions involving trigonometric functions to make integration or equation-solving more manageable.
**Proof Overview:**
To prove this identity, we can start by using the double-angle formula for cosine:
\[ \cos 2\theta = 2\cos^2 \theta - 1 \]
Rearrange the formula to express \(\cos^2 \theta\):
\[ 2\cos^2 \theta = 1 + \cos 2\theta \]
Now, divide both sides by 2:
\[ \cos^2 \theta = \frac{1 + \cos 2\theta}{2} \]
This completes the proof, verifying the identity as shown in the equation.
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