Question

If $\angle DAB={60}^O$ and $\angle DBA={50}^O$, then $\angle ACB=$?

• A. ${50}^O$
• B. ${60}^O$
• C. ${70}^O$
• D. ${80}^O$

Answer 1

The correct option is C ${70}^O$

In $\Delta ADB$, we have
$\angle ADC+\angle DBA+\angle DAB={180}^O$
$\angle DBA={180}^O-({60}^O+{50}^O)={70}^O$
As angles subtended by a chord at the circumference of the same segment are equal.
$\angle DBA=\angle ACB={70}^O$