How to use a boolean (yes/no) in a calculated column

I am trying to create a calculated column to convert a boolean into text so that I can use it to filter out results in a logic app. Based on research it seems that I should be able to do this with this forlmula.

=if([Proceesed]== true,'true','false')

I have tried various different version of this including substituting true with 1 and Yes but when I try to save the new column I get the technical error page. Any ideas on how to get this to work?