ABCD is a quadrilateral inscribed in a circle with centre O. If $\angle COD = 120$ degrees and $\angle BAC = 30$ degrees, then the value of $\angle BCD$ (in degrees) is

Question 52:
ABCD is a quadrilateral inscribed in a circle with centre O. If $\angle COD = 120$ degrees and $\angle BAC = 30$ degrees, then the value of $\angle BCD$ (in degrees) is

Answer: 90
Explanation:

$\angle COD = 120$ => $\angle CAD = 120/2 = 60$
$\angle BAC = 30$
$\angle BAD = \angle BAC + \angle CAD$ = 30 + 60 = 90.
$\angle BCD = 180 - \angle BAD$ = 180 - 90 = 90

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