Bira (geometria)

Geometrian, bira angeluak neurtzeko unitatea da, 360°-ren edo 2π radianen baliokidea. Angelu handiak neurtzeko erabiltzen da^[1].

Unitateak	Balioak
Birak	0	${\displaystyle {\tfrac {\tau }{12}}}$	${\displaystyle {\tfrac {\tau }{8}}}$	${\displaystyle {\tfrac {\tau }{6}}}$	${\displaystyle {\tfrac {\tau }{4}}}$	${\displaystyle {\tfrac {\tau }{2}}}$	${\displaystyle {\tfrac {3}{4}}\tau }$	${\displaystyle 1\tau \,}$
Gradu hirurogeitarrak	0°	30°	45°	60°	90°	180°	270°	360°
Radianak	0	${\displaystyle {\tfrac {\pi }{6}}}$	${\displaystyle {\tfrac {\pi }{4}}}$	${\displaystyle {\tfrac {\pi }{3}}}$	${\displaystyle {\tfrac {\pi }{2}}}$	${\displaystyle \pi \,}$	${\displaystyle {\tfrac {3\pi }{2}}}$	${\displaystyle 2\pi \,}$
Gradu ehundarrak	0g	${\displaystyle {\tfrac {100^{g}}{3}}}$	50g	${\displaystyle {\tfrac {200^{g}}{3}}}$	100g	200g	300g	400g