Question

If cos B = 3/5 , then what is the positive value of cos 1/2 B , in simplest radical form with a rational denominator?

Answer 1

Answer:

cos(B/2) = 2√5 / 5

Step-by-step explanation:

Use half angle formula:

cos²(B/2) = (1 + cos B) / 2

cos²(B/2) = (1 + 3/5) / 2

cos²(B/2) = (8/5) / 2

cos²(B/2) = 4/5

cos(B/2) = 2/√5

cos(B/2) = 2√5 / 5