How would I find cos(u/2) if sec u =13.465 and u is in Quadrant-IV (assume that 0<u<2π) ?

Question

cos(u/2)=___

Answer 1

these identities are helpful

cos(u) = 1 / sec(u)

cos(u/2) = ± √{[1 + cos(u)] / 2}

cos(u/2) = ± √({1 + [1 / sec(u)]} / 2)

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