Mapping Saw Wave That Is Between -1 And 1 To A Sine Wave
You can scale your sawtooth before you put it into the sine function, like so:

f=(-1:1/128:1)';

ramp = f * (length(f)-1)/length(f);  % Scale down to not include the last 1 into the sine
c1=repmat(ramp,1000,1);

c2=sin(pi*c1);   % -1 of saw wave maps to 0, 1 maps also to 0 


plot([c1 c2]);
%sound(c2, 44100);