3.1 Radian and Circle

3.1 Radians and Circles

Radian is another unit for measuring angles
The conversion is the following

$2{\pi ^r} = {360^ \circ }$
so
${\pi ^r} = {180^ \circ }$
so
${\frac{\pi }{2}^r} = {90^ \circ }$
and so on

Length of an Arc

The formula to find an arc is the following in degrees
$arc = 2\pi r \times \frac{\theta }{{360}}$
So in Radians we know that 360=2pi so in radian the formula is written like this
$arc = 2\pi r \times \frac{\theta }{{2\pi }}$

Area of a Sector

The formula for an sector is the following in Radians
$sector = \pi {r^2}\frac{\theta }{{2\pi }}$