General formula for interior angles of regular polygon with n sides =(n−2n)×1800
As we know Duodecagon has 12 sides.
So n=12
Magnitude of interior angle in degrees
=(12−212)×1800=1500
And, magnitude of interior angle in radians
=(12−212)×πc [∵ 1800=πc]
=(5π6)c
Hence, magnitude, in degrees and radians are
1500,(5π6)c respectively.