cho tam giac ABC vuong tai A co B= 30
a, tinh C
b, ve tia phan giac goc C cat canh AB tai D. tren canh CB lay diem Msao cho CA=CM. chung minh ΔACD=ΔMCD
c, qua C ve duong thang xy vuong goc voi CA. tu A ke duong thang song song voi CD cat xy o K. cm AK=CD
d, tinh goc AKC