# Trigonometry : Complete a Proof Using Sums, Differences, or Products of Sines and Cosines

## Example Questions

### Example Question #1 : Complete A Proof Using Sums, Differences, Or Products Of Sines And Cosines

True or false: .

False

Cannot be determined

True

False

Explanation:

The sum of sines is given by the formula .

### Example Question #2 : Complete A Proof Using Sums, Differences, Or Products Of Sines And Cosines

True or false: .

False

Cannot be determined

True

False

Explanation:

The difference of sines is given by the formula .

### Example Question #3 : Complete A Proof Using Sums, Differences, Or Products Of Sines And Cosines

True or false: .

True

Cannot be determined

False

False

Explanation:

The sum of cosines is given by the formula .

### Example Question #1 : Complete A Proof Using Sums, Differences, Or Products Of Sines And Cosines

True or false: .

Cannot be determined

True

False

False

Explanation:

The difference of cosines is given by the formula .

### Example Question #5 : Complete A Proof Using Sums, Differences, Or Products Of Sines And Cosines

Which of the following correctly demonstrates the compound angle formula?     Explanation:

The compound angle formula for sines states that .

### Example Question #6 : Complete A Proof Using Sums, Differences, Or Products Of Sines And Cosines

Which of the following correctly demonstrates the compound angle formula?     Explanation:

The compound angle formula for cosines states that .

### Example Question #7 : Complete A Proof Using Sums, Differences, Or Products Of Sines And Cosines

Simplify by applying the compound angle formula:      Explanation:

Using the compound angle formula, we can rewrite each half of the non-coefficient terms in the given expression. Given that and , substitution yields the following:  This is the formula for the product of sine and cosine, .

### Example Question #8 : Complete A Proof Using Sums, Differences, Or Products Of Sines And Cosines

Simplify by applying the compound angle formula:      Explanation:

Using the compound angle formula, we can rewrite each half of the non-coefficient terms in the given expression. Given that and , substitution yields the following:  This is the formula for the product of two cosines, .

### Example Question #9 : Complete A Proof Using Sums, Differences, Or Products Of Sines And Cosines

Using and the formula for the sum of two sines, rewrite the sum of cosine and sine:      Explanation:

Substitute for :  Apply the formula for the sum of two sines, :   ### Example Question #10 : Complete A Proof Using Sums, Differences, Or Products Of Sines And Cosines

Using and the formula for the difference of two sines, rewrite the difference of cosine and sine:      Explanation:

Substitute for :  Apply the formula for the difference of two sines, .    