The radius is R.

The center of the upper circle is me.

Angle OIB = (2x) degrees

BO=2rsinx

AO=(h^2+(pi-2x)*r)^( 1/2)

ao+bo=2rsinx+(h^2+(pi-2x)*r)^( 1/2)

- 1/2=(cos2x+ 1)(h^2+(pi-2x)*r)

Go beyond the equation. Your teacher is crazy.