Question

Define a radian measure.

Answer 1

Radian is used to measure angle where 1 radian equals to 57.3° angle subtended on centre of circle.

Actually, there are three systems which are used to measure angle
degree system, circular system and grade system.

in degree system ,1 right angle = 90° 1° = 60' , 1' = 60"
in grade system , 1 right angle =$100^g$,$1^g$ = 100' , 1' = 100"
in circular system,1 right angle = π/2 radian, 1° = π/180 radian .
because , π radian = 180°

Answer 2

Answer :

→ The Radian : One radian is the angle subtended at the centre of a circle by an arc equal in length to the radius of the circle is known as The radian. The value of 1 radian is 57.3°.

Formula : $\underline{\boxed{\sf{d \theta = \dfrac{ds}{r} radian}}}$