Answer:
√2 + √6 / 4
Step-by-step explanation:
We know cos(-θ) = cosθ.
Therefore, cos(-15°) = cos15°.
cos15° = cos(45 - 30)
- cos15° = cos45cos30 + sin45sin30
- cos15° = (1/√2)(1/2) + (1/√2)(√3/2)
- cos15° = 1/2√2 + √3/2√2
- cos15° = √3 + 1 / 2√2
- cos15° = (√3 + 1)(√2) / 4
- cos15° = √2 + √6 / 4
- Option 1
