Understanding Sum and Difference Identities

What is the formula for the cosine of the difference of two angles?

• cos(A - B) = sin A sin B - cos A cos B

• cos(A - B) = sin A cos B + cos A sin B

• cos(A - B) = cos A sin B + sin A cos B

• cos(A - B) = cos A cos B - sin A sin B

Why is it not necessary to memorize the tangent identities?

• They are not used in any calculations.

• They are not applicable to real-world problems.

• They can be derived using other identities and algebra.

• They are too complex to remember.

How can 75 degrees be expressed using known angles from the unit circle?

• 75° = 45° + 30°

• 75° = 60° + 15°

• 75° = 90° - 15°

• 75° = 45° - 30°

What is the sine of 30 degrees?

• 1

• √2/2

• √3/2

• 1/2

What is the cosine of 45 degrees?

• 1

• √2/2

• √3/2

• 1/2

In which quadrant is angle A if it is between 0 and π/2?

• Quadrant IV

• Quadrant I

• Quadrant II

• Quadrant III

What is the cosine of angle B if it is in quadrant II and has a cosine of 12/13?

• -5/13

• 12/13

• -12/13

• 5/13

What is the sine of angle A if its cosine is 3/5?

• 4/5

• -4/5

• 3/5

• -3/5

What is the result of adding 36/65 and -20/65?

• 56/65

• 20/65

• 16/65

• 36/65

What should you do if you have questions about the material?

• Ignore them and move on.

• Ask the teacher for clarification.

• Wait until the next class.

• Search online for answers.