由正弦定理得:BC/sinA=AC/sinB.
AC=(BC/sinA)*sinB.
=(8/sin135°)*sin30°.
=[8/(√2/2)]*(1/2).
=4√2.
又,由余弦定理,得:
AD^2=DC^2+AC^2-2DC*ACcosC.
=4^2+(4√2)^2-2*4*4√2*cos(15°).
=16+32-32√2[√2/4(√3+1)].
=48-16(√3+1).
∴AD=4√(2-√3).如果乱码就看下图:
由正弦定理得:BC/sinA=AC/sinB.
AC=(BC/sinA)*sinB.
=(8/sin135°)*sin30°.
=[8/(√2/2)]*(1/2).
=4√2.
又,由余弦定理,得:
AD^2=DC^2+AC^2-2DC*ACcosC.
=4^2+(4√2)^2-2*4*4√2*cos(15°).
=16+32-32√2[√2/4(√3+1)].
=48-16(√3+1).
∴AD=4√(2-√3).如果乱码就看下图: