Half angle of cosine given angle in degrees

The video tutorial covers the calculation of the cosine of 105 degrees using the half-angle formula. It explains the importance of determining the correct sign based on the quadrant and demonstrates how to simplify complex fractions. The tutorial emphasizes understanding when to use plus or minus in trigonometric formulas and provides a step-by-step approach to applying these concepts.

What is the purpose of the plus or minus sign in the half-angle formula?

• To indicate the angle is obtuse

• To show the angle is acute

• To specify the angle is a right angle

• To determine the quadrant of the angle

In which quadrant is the angle 105 degrees located?

• Fourth quadrant

• Second quadrant

• First quadrant

• Third quadrant

What is the cosine of 210 degrees?

• 1/2

• -sqrt 3 / 2

• sqrt 3 / 2

• -1/2

How do you simplify a complex fraction under a radical?

• Add the fractions

• Subtract the fractions

• Multiply by the reciprocal

• Multiply by 2/2

What is a valid way to rewrite a square root expression involving division?

• Add the terms under the square root

• Break up the square roots across division

• Subtract the terms under the square root

• Combine the terms under one square root