Triangle XYZ is isosceles with XY = XZ. Ray XW bisects angle YXZ, where W lies on YZ. Angle WXZ = 40°. Find the sum of angle XWY and angle XZY.
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Worked Solution
Step 1: Find angle YXZ.
XW bisects angle YXZ, and angle WXZ = 40°.
Angle YXZ = 2 × 40° = 80°
Step 2: Find the base angles of the isosceles triangle.
Since XY = XZ, triangle XYZ is isosceles, so angle XYZ = angle XZY.
Angle XZY = (180° − 80°) ÷ 2 = 100° ÷ 2 = 50°
Step 3: Find angle XWZ using the angle sum in triangle XWZ.
In △XWZ: angle WXZ + angle XZW + angle XWZ = 180°
40° + 50° + angle XWZ = 180°
Angle XWZ = 180° − 90° = 90°
Step 4: Find angle XWY.
Angles XWY and XWZ are supplementary (they form a straight line at W on YZ).
Angle XWY = 180° − 90° = 90°
Step 5: Find the required sum.
Angle XWY + angle XZY = 90° + 50° = 140°
Correct answer: 140°
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