In a given circle a central angle of 40° intercepts a chord of 6 cm. What is the circumference of the circle?

∠B = ∠A = 70°.

By the Law of Sines, the radius is | 6 | = | x |
→ | x |
= | 6 sin 70° | . |

sin 40° | sin 70° | sin 40° |

The circumference is 2r, or |
2 · 6 sin 70° | = | 12 · sin 70° | ≈ | 12 (3.14)(.94) |

sin 40° | sin 40° | .64 |

≈ 55.34 cm