Mark M. answered 04/12/16
Tutor
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Mathematics Teacher - NCLB Highly Qualified
cos 22.5
cos (45/2)
±√[(1 + cos 45) / 2]
±√[(1 + √2 / 2) / 2]
±√[(2 + √2) / 2] / 2
±√[(2 + √2) / 4]