Pre-Calculus - How to Evaluate Using the Double Angle Formula for Cosine

The video tutorial explains how to find the cosine of a double angle given the sine of an angle. It begins by introducing the problem and identifying the need to find the cosine of 2U. The instructor then discusses the selection of the appropriate formula, which is 1 - 2 sine^2(U), and explains why this formula is suitable for the problem. The tutorial proceeds with applying the formula by substituting the given sine value and performing the necessary calculations to arrive at the final result, which is -7/25.

What is the initial problem presented in the video?

• Finding the cotangent of a double angle

• Finding the sine of a double angle

• Finding the cosine of a double angle

• Finding the tangent of a double angle

Which formula is used to find the cosine of a double angle?

• 1 - 2 sine squared

• 1 + 2 sine squared

• 2 sine squared - 1

• 2 cosine squared - 1

Why are other trigonometric values not needed in this problem?

• Because the formula requires the cotangent value

• Because the formula only requires the sine value

• Because the formula requires the cosine value

• Because the formula requires the tangent value

What is the first step in the calculation process?

• Subtract the sine value from 1

• Multiply the sine value by 2

• Square the sine value

• Add the sine value to 1

What is the final result of the calculation?

• 7/25

• 32/25

• -32/25

• -7/25