Question

In the given figure, ABCD is a quadrilateral such that $DA\perp AB$ and $CB\perp AB$, x = y and EF || AD. Then $C{D}^2$ is equal to

• A. $2C{E}^2$
• B. $2D{E}^2$
• C. Both (a) and (b)
• D. None of these

Answer 1

The correct option is C

Both (a) and (b)

Given,
ABCD is a quadrilateral with $DA\perp AB$ and $CB\perp AB$
and EF || AD
$\Rightarrow EF||BC$
$\Rightarrow EF\perp AB$
Now, in $\Delta DAE$ and $\Delta CBE$,
$\angle DAE=\angle CBE$ [each ${90}^{\circ }$]
Also, $\angle DEA=\angle ECB$
And, $AE=BE$ [Given]
$\therefore \Delta DAE\cong \Delta EBC$ [by AAS congruence condition]
$\Rightarrow DE=EC$ [C.P.C.T.C.] ...(i)
Now, in $\Delta DEC$, right angled at E,
$D{E}^2+C{E}^2=D{C}^2$
$\Rightarrow 2D{E}^2=2C{E}^2=D{C}^2$ [From (i)]