Theorem of Equal Angles Subtended by Different Chords
In the given ...
Question
In the given figure, ∠ABC=69∘ and ∠ACB=31∘. Find ∠BDC.
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Solution
Given that ∠ABC=69∘ and ∠ACB=31∘.
Using angle sum property in △ABC, we have ∠BAC+∠ABC+∠ACB=180∘.
i.e., ∠BAC+69∘+31∘=180∘ ⟹∠BAC=180∘−100∘=80∘
Now, since the angles in the same segment are equal, ∠BAC=∠BDC. ∴∠BDC=80∘