To solve this problem, we need to use the fact that the sine and cosine functions are related to each other through the unit circle.
First, we need to find the angle whose cosine is equal to cos 50°. We can do this by drawing a unit circle and marking the angle 50° on the circle. Then, we draw a line from the center of the circle to the point on the circumference that corresponds to the angle 50°. This line will intersect the x-axis at a point that has the same x-coordinate as the cosine of 50°.
Next, we need to find the angle whose sine is equal to this x-coordinate. We can do this by drawing a perpendicular line from the point on the circumference to the y-axis. This line will intersect the y-axis at a point that has the same y-coordinate as the sine of the angle we are looking for.
Finally, we can find the angle by using the inverse sine function (also known as arcsine) to find the angle whose sine is equal to this y-coordinate.
Using this method, we find that the angle x is approximately 40.5°, which is closest to option (A) 40°. Therefore, the answer is (A) 40°.