calnum_sf - Solve with Fixed Significant Digits

calnum_sf solves mathematical expression with fixed significant figures.

% calnum_sf solves mathematical expression with fixed significant figures
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% inputs
% expression - your expression as a string
% numSF - number of significant figures
% method - uses following methods for rounding:
% 'round'
% 'fix'
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% outputx
% appVal the approximate result
% error the relative error
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% example
% [num,error]=calnum_sf('(2/9)*(9/7)*3-5*66*cos(log(3*5)-5)+3.5464*cos(6*sin(3)/5)^5',6,'round')
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% All copyrights goes to Mohammad Al-Fetyani
% University of Jordan