....

.....

dc ... edc

eb

..

dec=180-90-edc

eab=180-90-dec

...



ba=be*sin e/sin a

ea=be*sin b/sin a

... 3 3 ...

eb/de=ae/ce

ab/cd=eb/de

cosine rule

cd^2=ed^2+ec^2-(2*ed*ec*cos e

cd cb