Hello, snigdha!

Here's one solution . . . (There must be many others.)

In quadrilateral

Show that: .

Quadrilateral is a "kite".

Code:A o /|\ /θ|θ\ / | \ / | \ / | \ / | \ / θ' | θ' \ B o - - - + - - - o D * α | α * * α'|α' * * | * o C

Let

Then . where

Let

Then . where

Since is isosceles: .

. . Hence: .

And we have: .

Therefore: .

. . . . . . . . .

. . . . . .