Sum of sine functions in Matlab -

i have create function following definition:

function [ s1,s2,sums ] = sines( pts,amp,f1,f2 ) 

the output argument s1 row vector length (number of elements) equals pts. elements of s1 values of sine function when given equally spaced arguments start @ 0 , extend through f1 periods of sine. amplitude of sine wave equals amp. vector s2 same s1 except s2 contains f2 periods. vector sums sum of s1 , s2. if f2 omitted, should set value 5% greater f1. if f1 omitted also, should set 100. if amp not provided, should default 1. finally, if pts omitted well, should set 1000. have done following:

function [ s1,s2,sums ] = sines( pts,amp,f1,f2 )  if nargin == 3     f2  = f1 + (f1*0.05);     elseif nargin == 2     f1  = 100;     f2  = f1 + (f1*0.05);     elseif nargin == 1     amp = 1;     f1  = 100;     f2  = f1 + (f1*0.05); elseif nargin == 0     pts = 1000;     amp = 1;     f1  = 100;     f2  = f1 + (f1*0.05); end  t = 0:pts-1; s1   = amp * sin( 2*pi*f1.*t ); s2   = amp * sin( 2*pi*f2.*t ); sums = s1 + s2;  end 

the result should frequency modulated sine function, when plot sums not sine function, looks more sawtooth function, sharp. doing wrong?

you have forgotten normalize time-steps t between 0-1. f1 , f2 periods s1 , s2 respectively should have

t = (0:pts-1)/(pts-1);