Question

If ABCD is a cyclic quadrilateral, then $x$ = ___.

• A. ${120}^{\circ }$
• B. ${90}^{\circ }$
• C. ${100}^{\circ }$
• D. ${80}^{\circ }$

Answer 1

The correct option is C ${100}^{\circ }$

The sum of opposite angles of a cyclic quadrilateral is ${180}^{\circ }.$

$\Rightarrow \angle DAB+\angle DCB={180}^{\circ }$

$\Rightarrow {80}^{\circ }+x={180}^{\circ }$

$\Rightarrow x={100}^{\circ }$