IF condition in expression of Appian with AND and OR operators.

Hello, We are trying to compare two variables data inside 'IF' condition  on Appian interface but we are not sure how to apply AND and OR condition? Kindly let us know, how to add AND and OR operators in 'IF' condition. We tried using 2 different approaches but getting error 'The function 'if' [line 1] has 3 parameter(s), but instead passed 4 parameter(s).'

1. if(not(isnull(local!customeraccountnumber)) AND (local!selectedTab > 1)
, true(),
false())

2. if(not(isnull(local!customeraccountnumber)) && local!selectedTab > 1, true(), false())

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