Найдите cos a или sin a если: sin a =0,12 sin a =20/29 cos a= 3/7 sin a =0,8

1)sina=12/100
cos²a=1-144/10000=956/10000
cosa=√956/100
2)sina=20/29
cos²a=1-400/841=441/841
cosa=21/29
3)cosa=3/7
sin²a=1-9/49=40/49
sina=√40/7=2√10/7
4)sina=8/10
cos²a=1-64/100=36/100
cosa=6/10