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Question
In the given figure, ABCD is a cyclic quadrilateral. If ∠BCD = 100° and ∠ABD = 70°, find ∠ADB.
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Solution
It is given that ∠BCD = 100° and ∠ABD = 70°
We have to find the ∠ADB
We have
∠A + ∠C = 180° (Opposite pair of angle of cyclic quadrilateral)
So,
`angle A = 180° - 100°`
= 80°
Now in Δ ADB is `angle A ` = 80° and `angle ABD` = 70°
Therefore,
`angle A + angle ADB + angle ABD = 180°`
`80° + angleADB + 70° = 180°`
`angleADB = 180° - 150°`
= 30°
Hence, `angleADB` = 30°
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