Radian is a more advanced degrees measurement that is easier to use in trigonometry physics etc.
A full circle 360 degrees is 2pi radian.
We just need to find the ratio of 252 degrees to 360 degrees and multiply that by 2pi.
252/360*2pi(rad)
=126/180*2pi(rad)
=63/90*2pi(rad)
=21/30*2pi(rad)
=7/10*2pi(rad)
=7/5*pi (Radian)
Hope it helps and sorry for my bad grammar.