Some questions about sound(sine) waves.

Hi all.

I'm a music student and I've been trying to educate myself about acoustics lately.

I'm exploring the correlations between two pure sound waves.
This might be more of a mathemetical question rather than a physics one but anyways:

I want to know how can I calculate when/how freuqently this function:
^{f(x)=sin(x)+sin(1.05x)}
will be zeroed.

I wanna know this so I can now know frequent the pulses occur(by pulses I mean the fluctuating volume of the sound).

Also, what is the proper way to define the sine function of , say, 440Hz?
Sin(440) ?

Thx in advance, hope I'm not too noobish :)