Posted by **sam** on Sunday, October 2, 2011 at 5:12pm.

Find all solutions to the equation

2cos(2x) = x + 1, correct to 4 decimal places.

- trig -
**Steve**, Monday, October 3, 2011 at 5:32am
2 cos(2x) never gets out of the range [-2,2]

So, whenever |x+1| > 2, there are no solutions.

That means all solutions are in [-3,1]

A little Newton-Raphson should work nicely here, or a bisection method.

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