To rotate a point \((x, y)\) by \(90^\circ\) counterclockwise about the origin, you can use the transformation:
\[ (x, y) \to (-y, x) \]
Now, let's apply this transformation to the point \(E(5, 3)\):
- Identify the coordinates of E: \(E(5, 3)\).
- Apply the transformation:
- New x-coordinate: \(-y = -3\)
- New y-coordinate: \(x = 5\)
Thus, the coordinates of point \(E'\) after the rotation will be:
\[ E'(-3, 5) \]
Therefore, the coordinate of \(E'\) is \((-3, 5)\).