notam O centrul cercului m(F)=180⁰-30-60⁰=90 m(<EOF)=m(<EDF) x2=30⁰ x 2=60⁰ m(<DOE)=m(<DFE) x2=90⁰ x 2=180⁰ m(<DOF)=m(<DEF) x2=60⁰ x 2=120⁰ Lcercului=2πr=2×18π=36π cm
L(DE) = 36π × 180⁰/360⁰=18π cm L(EF) = 36π × 60⁰/360⁰=6π cm L(DF) = 36π × 120⁰/360⁰=12π cm