two circles are tangent externally to a third circle at A and are tangent internally to a third circle at A and D. if BC is the common internal tangent and equal to 20 cm. find the area of the shaded portion
two circles are tangent externally to a third circle at A and are tangent internally to a third circle at A and D. if BC is the common internal tangent and equal to 20 cm. find the area of the shaded portion