How to evaluate for cosine using the sum and difference identities

The video tutorial covers the selection of angles within the first quadrant for trigonometric calculations, focusing on the cosine of U-V formula. The instructor explains the importance of parentheses in the formula and demonstrates its application using specific angles. The tutorial also discusses simplifying trigonometric expressions and provides strategies for tackling multiple choice questions, emphasizing the need to understand different forms of answers.

Why does the teacher prefer to work within the first quadrant?

• It avoids negative angles.

• It simplifies calculations.

• It is a personal preference.

• It is a requirement for all trigonometric problems.

What is the significance of parentheses in the cosine angle subtraction formula?

• They indicate multiplication of angles.

• They help in distinguishing between positive and negative angles.

• They are used to group terms for addition.

• They are optional and can be omitted.

What does the plus-minus rule in the cosine formula indicate?

• Always add the angles.

• It is irrelevant to the formula.

• Add when subtracting angles and subtract when adding angles.

• Subtract when subtracting angles and add when adding angles.

What is the cosine of 30 degrees?

• sqrt 3 / 2

• sqrt 2 / 2

• 0

• 1/2

What is the sine of 45 degrees?

• 1

• sqrt 3 / 2

• sqrt 2 / 2

• 1/2

How can the expression for cosine of 30 degrees minus 45 degrees be simplified?

• By factoring out sqrt 2 / 2

• By adding the angles

• By using the sine addition formula

• By converting to radians

What is a common strategy for solving multiple-choice questions involving trigonometric expressions?

• Use a calculator for verification.

• Factor and multiply to match the given options.

• Convert all angles to radians.

• Always choose the simplest form.