sin C = √[ 1 - ( cos C )^2] = √5/5.
sin B = sin (135度 - C) = 3√10/10.
由正弦定理可得：
BC/sin A = AC/sin B,由此得出：BC = AC sin A/sin B = 5√2/3.
类似可得：AB/sin C = AC/sin B,得出：AB = 2√5/3；这样,AD = √5/3.
利用余弦定理即可求出中线 CD.