∵AC=4,AB=5,∠C=90°,
∴BC=
AB 2 - AC 2 =
25-16 =3,
∴CD=BC+BD=8,
AD=
AC 2 +C D 2 =4
5 ,
∴sinD=
AC
AD =
5
5 ,cosD=
CD
AD =
2
5
5 .
∵AC=4,AB=5,∠C=90°,
∴BC=
AB 2 - AC 2 =
25-16 =3,
∴CD=BC+BD=8,
AD=
AC 2 +C D 2 =4
5 ,
∴sinD=
AC
AD =
5
5 ,cosD=
CD
AD =
2
5
5 .