SOLUTION: If cos A = -4/5 for angle A in Quadrant II, find cos A/2

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Question 1098264: If cos A = -4/5 for angle A in Quadrant II, find cos A/2
Answer by Boreal(15235) About Me  (Show Source):
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cosine of A/2 is +/- sqrt of (1-(4/5))/2=sqrt (1/5)/2=sqrt (1/10)=0.316
A is arc cos (-.8)=143.13 degrees
A/2 is arc cos (0.316)=71.57 degrees