engineering mathematics MCQ #5539

What is the value of cos(165°)?

engineering mathematics MCQ #5539

  1. Question 1

    Q1. What is the value of cos(165°)?

    • A) -(√2 + √6)/4
    • B) (√2 + √6)/4
    • C) -(√6 + √2)/4
    • D) (√6 - √2)/4

    Answer: -(√2 + √6)/4

    Explanation: Using cos(A + B) = cos(A)cos(B) - sin(A)sin(B), cos(165°) = cos(120° + 45°) = cos(120°)cos(45°) - sin(120°)sin(45°) = (-1/2)(√2/2) - (√3/2)(√2/2) = -(√2 + √6)/4.