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

The video tutorial explains how to find the cosine of the difference between two angles, 225 degrees and 30 degrees, using the cosine difference formula. It involves evaluating the cosine and sine of each angle using the unit circle, then applying these values to the formula. The tutorial concludes with simplifying the expression to find the final result.

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

• To find the tangent of the difference between two angles

• To find the sine of the difference between two angles

• To find the cosine of the difference between two angles

• To find the sum of two angles

What are the cosine and sine values for 30 degrees?

• cosine: 1/2, sine: sqrt 3 / 2

• cosine: sqrt 3 / 2, sine: 1/2

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

• cosine: sqrt 2 / 2, sine: sqrt 2 / 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 3 / 4

• sqrt 6 / 4

• -sqrt 3 / 4

• -sqrt 6 / 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