Ac is tangent to circle O at A. The diagram is not drawn to scale. If m by=52 degrees what is m yac?
A. 38°
B.64°
C.78°
D.104°

ANSWER
A. 38°
EXPLANATION
The tangent, AC to the circle meets the diameter AB to the circle at right angle.
This implies that,
[tex]m \angle BAY + m \angle YAC = 90 \degree[/tex]
Substitute the given angle:
[tex]52 \degree + m \angle YAC = 90 \degree[/tex]
[tex]m \angle YAC = 90 \degree - 52 \degree[/tex]
[tex]m \angle YAC = 38 \degree[/tex]
Using the tangent theorem and the inscribed angle theorem, m∠YAC is: A. 38°
According to the tangent theorem, a right angle (90°) is formed at the point of intersection between the radius and the tangent of a circle.
m∠BAY = m(BY) = 52° (inscribed angle theorem)
m∠BAC = 90° (tangent theorem)
m∠YAC = m∠BAC - m∠BAY
Substitute
m∠YAC = 90 - 52 = 38°
Learn more about the tangent theorem on:
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