# Radian

See how to write and use the angle in radian measure.

5 examples and their solutions.

## Radian

### Formula

(rad) = (°)⋅π180

Radian is a way to write the measure of an angle.180° = π

Unit: rad (can be omitted)

### Example

30° → rad?

Solution θ = 30⋅π180

= π6

= π6

Close

### Example

π4 → °?

Solution θ⋅π180 = π4

θ180 = 14

θ = 1804

= 45°

θ180 = 14

θ = 1804

= 45°

Close

## Mostly Used Angles in Radian

### Formula

° | rad |
---|---|

0° | 0 |

30° | π6 |

45° | π4 |

60° | π3 |

90° | π2 |

180° | π |

270° | 3π2 |

360° | 2π |

## Length of an Arc (Radian)

### Formula

l = rθ

### Example

Length of AB = ?

Solution l = 6⋅2π3

= 3⋅2π

= 6π

Close

## Area of the Sector of a Circle (Radian)

### Formula 1

A = 12r

^{2}θ

### Example

Area?

Solution A = 12⋅6

^{2}⋅2π3

= 6π⋅2

= 12π

Close

### Formula 2

A = 12rl

### Example

Area?

Solution A = 12⋅4⋅3π

= 2⋅3π

= 6π

Close