Question

AC is tangent to circle O at A

If mBY = 64°, what is the m∠YAC?

a. 58°
b. 180°
c. 26°
d. 22°

Answers

GPT-4o mini
In the configuration where line AC is tangent to circle O at point A, and you have an angle m∠BY (which appears to be an external angle created by lines AC and BY), you can use the tangent-secant angle theorem.

The tangent-secant angle theorem states that the angle formed by a tangent and a chord through the point of tangency is equal to half the measure of the arc intercepted by the chord.

Given:
- \( \text{m}BY = 64^\circ \)

Here, angle BY subtends the arc that includes point A. The angle ∠YAC is the angle formed between the tangent (AC) and line (AY) at point A. According to the theorem:

\[
m\angle YAC = \frac{1}{2} m\text{arc} YB
\]

If we assume that arc YB is the arc created by angle BY, then we have:

\[
m\angle YAC = \frac{1}{2} \times 64^\circ = 32^\circ
\]

However, it appears that we may need to reconsider what m∠YAC actually refers to, as the response options don't include 32°. Based on how the angles are intended to interact, if BY equals 64° and if YAC is somehow related to some part of a triangle created or relevant calculations, we can reevaluate.

Assuming \(m∠YAC\) directly relates to the angle measure given, and looking at the question options again, we'd find that while the math suggests 32° as calculated, it might point towards another geometric relationship requiring adjustment or additional circles/points.

Without other information or figures, from the common adjustment to reach a correct answer fitting one of the options given, the most appropriate angle at face value interpreted often might be confirming expectations or known elements directly yielding towards:

If additional key sections were included in setup or geometry which might not have directly translated and instead a different route was sought to re-check options of remaining degrees, they also might be used.

### Conclusion:
In geometry problems like this, double-check to ensure all intersections or components are factored correctly. The calculation here does yield 32°, and as listed options (58°, 180°, 26°, 22°), option alignment may need exploration depending on the specific angle definitions used throughout the theorem basis applied. Please feel free to clarify any further specific context or additional angles, as I can assist better in regrouping overall as needed or illustrative connections further.