The x-intercept of a function is the value of x when y is 0. So let's set sin(x) equal to zero. When does sin(x) equal zero? Based on the unit circle, you know that sin(0) is 0, so that is one x-intercept. You also know that sin(pi) is 0. Basically, every time x, starting from zero, increases or decreases by a multiple of pi, sin(x) is still zero. The answer can be represented by x=n*pi; where n=any integer.
