In the complex plane, multiplying a given function by i rotates it anti-clockwise by how many degrees?

The answer is 90 degrees because multiplying a given function by i in the complex plane can be understood as multiplying the vector representing the function by a unit vector representing i, which is located at an angle of 90 degrees counterclockwise from the positive real axis. This multiplication effectively rotates the function vector by 90 degrees counterclockwise, resulting in a new vector representing the function at a new angle of 90 degrees counterclockwise from its original position. Thus, the function is rotated by 90 degrees anticlockwise when multiplied by i in the complex plane.