Answer:
Cos 68
Explanation:
Given the expression 2cos² 34° - 1, we are to expression as a single trig ratio.
Let the angle be theta
Recall that sin²theta + cos²theta = 1
sin²theta = 1 - cos²theta ... 1
also Cos 2theta = Cos²theta - sin²theta ... 2
Substitute 1 into 2
Cos 2theta = Cos²theta - (1-cos²theta)
Cos 2theta = Cos²theta - 1 + cos²theta
Cos 2theta = 2Cos²theta - 1
Replace theta with 34
Cos 2(34)= 2Cos²(34)- 1
Cos 68 = 2Cos²(34)- 1
Hence the single trig expression is Cos 68