Question

Using the formula cos A=+,
1+ cos2A
2
find the value of cos 134/2

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Answer 1

Using the formula cos A=+,

1+ cos2A

2

find the value of cos 134/2

Answer:

(√3 + 1) ÷ 4

Step-by-step explanation:

cos A = root 1+ cos2A / 2

cos A =√ (1+ cos2A) / 2

cos 15° =√ (1+ cos 30°) / 2

cos 15° =√ (1+ √3/2) / 2  =√ (1+ 2√3/4) / 2  √ (4+ 2√3/√4 * 2

cos 15° = (√3 + 1) ÷ 4