Orthocentre angle relation – ∠BOC = 100° (O is orthocentre):\nIn triangle ABC, O is the orthocentre. If ∠BOC = 100°, find ∠BAC.

Difficulty: Medium

100°
180°
80°
200°
None of these

Correct Answer: 80°

Explanation:

Introduction / Context:
A key property: in any triangle, the angle ∠BHC at the orthocentre H equals 180° − ∠A. Here, O plays the role of H.

Concept / Approach:
Thus ∠BOC = 180° − ∠A ⇒ ∠A = 180° − ∠BOC.

Step-by-Step Solution:

∠A = 180° − 100° = 80°.

Final Answer:
80°

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