Posted by **tomas** on Tuesday, May 31, 2011 at 7:43pm.

verifying a solution.

4cos^2 2x-2=0

- trig -
**Reiny**, Tuesday, May 31, 2011 at 8:43pm
4cos^2 2x-2=0

cos^2 (2x) = 1/2

cos (2x) = ± 1/√2

2x = 45° or 2x = 135° or 2x = 225° or 2x = 315°

x = 22.5°, 67.5°, 112.5°, 157.5, ...

the period of cos 2x is 180°, so adding 180° to any of the above answers will produce a new answer.

So there is an infinite number of solutions.

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