little circle at top right corner of a square

[lev888]

Using the diagram in post 20:
\(\displaystyle tan\text{ θ} = \frac{4}{12}\)
From the tangent of double angle identity: \(\displaystyle tan\text{ 2θ} = \frac{3}{4}\)
Therefore ED = 12, area = 160.

 

[The Highlander]

Using the diagram in post 20:
\(\displaystyle tan\text{ θ} = \frac{4}{12}\)
From the tangent of double angle identity: \(\displaystyle tan\text{ 2θ} = \frac{3}{4}\)
Therefore ED = 12, area = 160.

Very slick!
Reducing the whole thing to just one line!
(I just followed the (slightly) more tortuous route so that any of my 5th year Maths pupils could follow it. )