Question

What is the y-value of sin(x) when x = 30°

Answer 1

The sine of 30° is  0.5 .

Angles don't have y-values, and neither do their sines.  But
IF you draw a graph of the sine function, AND the angles
(the independent variable) are marked off on the x-axis of
the graph, AND the value of the sine function of each angle
(the dependent variable) is marked off on the y-axis of the
graph, THEN the y-value corresponding to the angle of 30°
would be displayed as 0.5 .