In the diagram, chords KM, MN and KN are drawn in the circle O with centre O - NSC Mathematics - Question 11 - 2017 - Paper 2
Question 11
In the diagram, chords KM, MN and KN are drawn in the circle O with centre O. PNQ is the tangent to the circle at N.
Prove the theorem which states that MNQ = K.
Worked Solution & Example Answer:In the diagram, chords KM, MN and KN are drawn in the circle O with centre O - NSC Mathematics - Question 11 - 2017 - Paper 2
Step 1
Prove that angle MNR = 90°
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Answer
Since PNQ is a tangent to the circle at point N, by the property of tangents, we have:
∠MNR=90°
This is because the tangent line at any point of a circle is perpendicular to the radius drawn to that point.
Step 2
Establish the relationship between angles in a semi-circle
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Answer
Using the property of angles subtended by a chord in a semi-circle:
∠MNQ=∠MKN
Since both angles subtend the same chord MN, we can conclude that:
∠MNQ+∠MNR=180°
Step 3
Final conclusion
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Answer
Now substituting the value of ( \angle MNR ):
∠MNQ+90°=180°
Thus,
∠MNQ=90°
Since MNQ and K are both equivalent angles, we conclude that: