# Abcd Is a Cyclic Quadrilateral In ∠Bcd = 100° and ∠Abd = 70° Find ∠Adb. - Mathematics

Short Note

ABCD is a cyclic quadrilateral in   ∠BCD = 100° and ∠ABD = 70° find ∠ADB.

#### Solution

It is given that, ∠BCD = 100° and ABD = 70°

As we know that sum of the opposite pair of angles of cyclic quadrilateral is 180°.

$\angle ADC + \angle ABC = 180°$
$\Rightarrow 180° - 80° + 180° - x = 180°$
$\Rightarrow x = 100°$

In ΔABD we have,

$\angle DAB + \angle ABD + \angle BDA = 180°$
$\Rightarrow \angle BDA = 180° - 150° = 30°$

Hence,  angle ABD = 30°

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#### APPEARS IN

RD Sharma Mathematics for Class 9
Chapter 15 Circles
Exercise 15.5 | Q 18.3 | Page 103