To find the arc measure of when triangle is inscribed in a circle with diameter and the angle at vertex measures , we can use the properties of inscribed angles.
The inscribed angle intercepts the arc . According to the properties of inscribed angles, the measure of an inscribed angle is half the measure of the arc it intercepts.
Let be the measure of arc . According to the relationship:
Given that , we can set up the equation:
To find , we multiply both sides by 2:
Thus, the measure of the arc is .
There may be a misunderstanding with the response of , as is the correct measure for arc .
If you're looking for the measure of the remaining arc (which may be referred to if a larger angle is being considered), the total circumference of a circle is . Therefore, if the full circle is :
But as per the original question focusing on arc , the arc measure of is .