is a tangent to a circle at point . is a triangle inscribed in the circle. If angle and angle , calculate the size of angle .
Answer and explanation
Correct answer: A.
- Step 1: Apply the Alternate Segment Theorem: the angle between tangent and chord equals the angle subtended by chord in the alternate segment: .
- Step 2: Use the triangle angle sum theorem in : the interior angles of a triangle sum to : .
- Step 3: Substitute the known angles: .
Answer
.
Why not the others: is angle ; is angle ; subtracts incorrectly ().
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