The exterior angle of a triangle is 140°. One of the non-adjacent interior angles is 65°. What is the other non-adjacent interior angle?
A40°
B65°
C75°
D115°
Explanation
📌 Step 1: Recall the Exterior Angle Theorem The exterior angle of a triangle equals the sum of the two non-adjacent interior angles.
📌 Step 2: Set up the equation exterior angle = angle A + angle C 140° = 65° + angle C
📌 Step 3: Solve angle C = 140° − 65° = 75°
💡 Tip: The Exterior Angle Theorem is a shortcut! You don't need to find the interior angle at B first. The exterior angle always equals the sum of the two "remote" interior angles.
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