You need to use pow
method of math.h from C-language.
antilog = pow(10, number) ;
This will give you antilog of number
by base10
Side Note:
As you are creating a Scientific Calculator and you would be needing Base for the number.
EDIT:
double number=74.5;
double logOfNumber=log10(number);
double antilog = pow(10, logOfNumber) ;
NSLog(@"%lf",antilog);
Output: 74.500000
10
solved How to find out antilog [closed]