Final answer:
The principal angle of theta when it is 50 degrees is simply 50 degrees, as it already falls within the range of 0° to 360°.
Step-by-step explanation:
To find the principal angle when theta is 50 degrees, you do not need to perform any additional calculations, as principal angles are defined as angles measured from the positive x-axis in a counter-clockwise direction whose measures are between 0° and 360°. A theta value of 50 degrees already falls within this range, so 50 degrees itself is the principal angle.