First we imagine triangle. Triangle vertices are: xy coordinate center, point (4,3) and projection of that point on x axis (x = 4). Because angle is in standard position, just from knowing (4,3) coordinates we know 2 of triangle sides and we can find its hypotenuse which will be marked as "h":

Now the sinq is:
sinq = 3/5 because of definition of sin.
sin = opposite side of triangle/hypotenuse.
answer is 3/5