Angle OGK (\(x\)) = angle OKG because triangle GOK is also isosceles. Lengths OK and OG are also both radii. Angle GOH = \(180 - 2y\) (because angles in a triangle add up to 180°) Angle GOK ...

Angle OGH (\(y\)) = angle OHG because triangle GOH is also isosceles. Lengths OH and OG are also both radii. Angle GOH = \(180^\circ - 2y\) (because angles in a triangle add up to 180°).