The main idea is using the Pythagorean formula to find the length of line segment [tex]DB[/tex].
Alr so you use the formula [tex]A^2 + B^2 = C^2[/tex]
[tex]C^2[/tex] is already given and is [tex]2\sqrt{5}[/tex]
and [tex]A^2[/tex] is [tex]3\sqrt{2}[/tex]
So using algebraic rules you'll get [tex]B[/tex] as:
[tex]\sqrt{2}[/tex]
Now using the formula: [tex]\frac{1}{2} b * h[/tex], you can find the area of tri ABD and CBD which would be [tex]3[/tex] and [tex]1[/tex] so add them up and you get [tex]4[/tex]!
