The angle (1/2)π radians is equivalent to 90°. Since angles are measured counterclockwise from the +x axis, an angle of 90° (or π/2 radians) is in the direction of the +y axis.
Your polar coordinates of 1∠(π/2) specify a point 1 unit up from the origin on the y-axis. The coordinates of that point are (x, y) = (0, 1).
