Pre-Calculus - Using the difference of angles for cosine to evaluate for an angle cos(225-30)

What is the purpose of using the cosine difference formula in this problem?

• To find the sine of the difference between two angles

• To find the sum of two angles

• To find the cosine of the difference between two angles

• To find the product of two angles

What are the cosine and sine values for 30 degrees?

• cosine: -sqrt 2 / 2, sine: -sqrt 2 / 2

• cosine: sqrt 2 / 2, sine: sqrt 2 / 2

• cosine: sqrt 3 / 2, sine: 1/2

• cosine: 1/2, sine: sqrt 3 / 2

What are the coordinate points for 225 degrees on the unit circle?

• (1/2, sqrt 3 / 2)

• (-sqrt 2 / 2, -sqrt 2 / 2)

• (sqrt 3 / 2, 1/2)

• (sqrt 2 / 2, sqrt 2 / 2)

What is the result of multiplying the cosine of 225 degrees and the cosine of 30 degrees?

• sqrt 6 / 4

• -sqrt 3 / 4

• -sqrt 6 / 4

• sqrt 3 / 4

What is the final simplified expression for the cosine of 225 degrees minus 30 degrees?

• -sqrt 3 - 1

• -sqrt 3 + 1

• sqrt 3 - 1

• sqrt 3 + 1