Write the Product as a Sum $\cos 7 x \cos 3 x$

question 97

Multiple Choice

Write the product as a sum. $\cos 7 x \cos 3 x$

• A) \(\cos 7 x + \cos 3 x\)
• B) \([ \cos 7 x + \cos 3 x ] / 2\)
• C) \([ \cos 10 x + \cos 4 x ] / 2\)
• D) \(- [ \cos 5 x + \cos 2 x ] / 2\)
• E) none of these