15. If m arc BY = 40 degrees, what is m angle YAC? the figure is not drawn to scale.

If [tex]m\widehat{BY}=40^\circ[/tex], then the central angle [tex]\angle BOY[/tex] has the same measure, and by the inscribed angle theorem we have
[tex]m\angle BAY=\dfrac12m\angle BOY=20^\circ[/tex]
It's impossible to know what the measure of angle YAC is from this information alone, but assuming AC is tangent to the circle, then angles BAY and YAC are complementary, so that [tex]m\angle YAC=70^\circ[/tex].
The line AC is the tangent of the line, and the measure of the angle YAC is 70 degrees
The measure of the arc is given as:
Arc BY = 40 degrees
The measure of angle BAY is calculated using:
BAY = 0.5 * BY
This gives
BAY = 0.5 * 40
BAY = 20
The angle at a tangent is 90 degrees.
This means that:
BAY + YAC = 90
Substitute 20 for BAY
20 + YAC = 90
Subtract 20 from both sides
YAC = 70
Hence, the measure of the angle YAC is 70 degrees
Read more about tangent lines at:
https://brainly.com/question/6617153
#SPJ2