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Half Angle Identities

cosx = 7/25
greater than 270 deg and less than 360
Determine cos 1/2x
a. -7rt2/10
b. 7rt2/5
c.7/25
d.-4/5
I get 7rt2/5 Is this correct??

1 answer

Oops, brain fart ... answer is -4/5 i guess it was a long day ...
thanks anyway ..
Don
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