Question

For what x-value(s) does sin(x) = -1?

Answer 1

Did you learn about the unit circle?

Answer 2

kinda

Answer 3

Short summary: Draw a circle with a radius of one centered at the origin. The x values along the circle correspond to cos(a), the y values correspond to sin(a). And "a" is the angle drawn when you starting at the x-axis and swipe through counter-clockwise.