If an angle $\mathrm{AFE}$ is in standard position and its terminal side passes through the point $(0,1)$ on the unit circle, what is the measure of angle $\mathrm{AFE}$ in degrees?

• A. $81°$
• B. $99°$
• C. $79°$
• D. $90°$

Answer: (D)

Verified step by step guidance

1. Recall that an angle in standard position has its vertex at the origin and its initial side along the positive x-axis, with the terminal side rotating counterclockwise from there.
2. Since the terminal side passes through the point (0, 1) on the unit circle, note that this point lies exactly on the positive y-axis.
3. On the unit circle, the coordinates (x, y) correspond to (cos \theta, sin \theta), where \theta is the angle in standard position.
4. Given the point (0, 1), we have cos \theta = 0 and sin \theta = 1, which corresponds to an angle where the terminal side is pointing straight up.
5. Identify the angle \theta in degrees whose cosine is 0 and sine is 1, which is the angle measure of angle AFE.