Find a function

Hi everybody
I want to know what's the function of sinusoidal curve but with sharp peaks both positive and negative? In the other word, peaks (positive and negative) be as follows:
/\/\/\/\/\/\/\

Thanks so much.

Your question doesn't make enough sense to give an answer. You tell us you want a sine curve, but with features that make it not a sine curve. Maybe you mean a sawtooth wave? Or do you mean that it's like a sine wave where all the "peaks" appear above the x-axis? That might be $|\sin x|$ or even $\sin^2 x$ maybe.

I mean sawtooth wave, please give an answer that what's the function of the sawtooth wave as distance of between teeth be "a" and height of ones be "b" as follows:

/\/\/\/\/\/\/\ |b
_
a

Thank you so much.

It's a piecewise continuous periodic function which you can express as the combination of two linear functions of the form $y = \frac{2b}{a}x, y=-\frac{2b}{a}x$ if I understand your picture correctly.

You should be able to figure out the details yourself.