Which of the following is a property of an angle in standard position on the coordinate plane?

• A. Its initial side lies along the positive $x$-axis.
• B. Its terminal side always lies in the first quadrant.
• C. It must have a measure less than $90°$.
• D. Its initial side lies along the negative $y$-axis.

Answer: (A)

Verified step by step guidance

1. Understand what it means for an angle to be in standard position: its vertex is at the origin of the coordinate plane, and its initial side lies along the positive x-axis.
2. Recall that the initial side of an angle in standard position is fixed along the positive x-axis, while the terminal side can rotate to any position around the origin.
3. Recognize that the terminal side of the angle is not restricted to any specific quadrant; it can lie in the first, second, third, or fourth quadrant depending on the angle's measure.
4. Note that the angle measure in standard position can be any real number, positive or negative, and is not limited to being less than 90 degrees.
5. Conclude that the defining property of an angle in standard position is that its initial side lies along the positive x-axis.