svp j'ai pas compris A.B.C

a)
[tex]Sin \angle{MNO} = \frac{OM}{ ON} = \frac{2}{5} = 0,40\\\angle{MNO} = Sin^{-1} 0,40 = 23,578^0=24^0[/tex]

b)
[tex]Sin \angle {MNO} = \frac{OM}{ON} = \frac{1,2}{2} = 0,60\\\angle{MNO} = Sin^{-1} 0,60 = 36,87^0=37^0.[/tex]

c)
[tex]Tan \angle{MNO} = \frac{OM}{ON} =\frac{ 5}{7} = 0,7143\\\angle{MNO}=Tan^{-1}0,7143=35,54^0=36^0[/tex]

d)

[tex]Cos \angle{PON} = Cos 55^0 = \frac{ON}{OP}\\ON=8,5*Cos\ 55^0 = 4,875cm\\\\Sin \angle{MNO} = \frac{OM}{ON}=\frac{2}{4,875}= 0,410\\\angle {MNO} = Sin^{-1}0,410 = 24,2^0=24^0.[/tex]