SOLUTION: Need help - Solve cos(x/4) = 1/2 in interval (-6pi,4pi).

We'll take each one individually.



Multiply through by 4



in interval (-6pi,4pi)}}}



Multiply all three sides by 3



Subtract  from all three sides:



Divide all three sides by 





The only integer between those values is k = 0.

So one solution is 





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For the other one,



Multiply through by 4



in interval (-6pi,4pi)}}}



Multiply all three sides by 3



Subtract  from all three sides:



Divide all three sides by 







The only integer between those values is k = -1.

So the other solution is 













Answer:   and 

Edwin