The diagonals are equal and split a rectangle into four isosceles triangles. The diagonals do not meet at right angles. Since each corner of a rectangle is 90°, then the smaller top left corner ...

Each angle at the centre is \(72^\circ\) as the \(360^\circ\) at the centre is split into five parts. This means that in each triangle we have \(108^\circ\) left for the two angles lying on the ...