math
posted by Anonymous .
cosA= 5/9 find cos1/2A
are you familiar with the halfangle formulas?
the one I would use here is
cos A = 2cos^2 (1/2)A  1
5/9 + 1 =2cos^2 (1/2)A
14/9 =2cos^2 (1/2)A
cos (1/2)A = √(7)/3
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