Question

In the given figure, ABCD is a cyclic quadrilateral. If ∠BCD = 100° and ∠ABD = 70°, find ∠ADB.

Answer 1

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°