In a circle, an inscribed angle is an angle formed by two chords that share an endpoint on the circle. The measure of the inscribed angle is half the measure of the arc that it intercepts.
Given that triangle XYZ is inscribed in a circle with diameter XZ, and the angle measure at point X (∠XYZ) is 59 degrees, we can analyze the situation as follows:
Since XZ is a diameter, by the inscribed angle theorem, the angle Y (∠XYX) opposite to the diameter will be a right angle (90 degrees). Therefore, we can deduce that the other angle in the triangle, ∠YZX, can be found.
The angles in triangle XYZ sum up to 180 degrees:
\[ \angle XYZ + \angle YZX + \angle ZXY = 180^\circ \]
Let’s denote:
- ∠XYZ = 59 degrees (angle at X)
- ∠ZXY = ∠Y
- ∠YZX = ∠Z
Since ∠XYZ is 59 degrees, we can express the other angle ∠YZX (let's denote it as z):
\[ 59^\circ + z + \angle Y = 180^\circ \]
However, we need to find the arc measure of XY.
The inscribed angle ∠YZ (formed by points Y and Z) is equal to half the measure of arc XZ. Given that XZ is a diameter of the circle and using the fact that angles inscribed in a semicircle are right angles, we have:
\[ \text{arc XZ} = 180^\circ \]
We can find the measure of arc XY by recognizing that angle Y (∠Y) is inscribed in the circle and intercepts arc XY. Thus:
\[ \angle Y = \frac{1}{2}(\text{arc XY}) \]
The inscribed angle at Y (∠Y) can be determined from:
\[ \angle Y = 180^\circ - 59^\circ - (arc Z)+ \text{arc XY}= 180 - \angle X - \angle Z \]
Since it's a triangle and we already deduce that ∠X (X) + ∠Y (Y) + ∠Z (Z) = 180, making the deductions knowing one outside can be difficult, but you guessed right that a complete arc at Z ends up bringing that as well back.
Hence to develop simply: Each angle on the base of the triangle’s properties will govern the intersecting vertex angle endings. Hence, without full breakdowns towards Z aspect, re-evaluating XY will revert back through diameter handling.
Thus considering:
- Arc XY = ∠Z = 2(90 - 59) = 2(31) = 62°
This concludes with result:
- Arc measure of XY = 62 degrees.