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  1. What is the value of cos 105°?
    1. 1 - √3
      2√2
    2. 1 + √3
      2√2
    3. √3 - 1
      2√2
    4. √3
      2√2
Correct Option: A

cos 105° = cos(60° + 45°)
= cos 60° × cos 45° – sin 60° × sin 45°
[∵ cos (A + B) = cosA cosB – sinA sinB]

=
1
.
1
 -
√3
.
1
 =
1 - √3
2√22√22√2


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