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26 October, 06:35

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

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  1. 26 October, 08:59
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    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
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