9

, . , (h=ab ).

ABCD-. AC;BD-

: ADC-. (AC=d2; AD=h; DC=b) =>d2=h+b

ADB- . (AD=h; AB=a; DB=d1)=> d1=a+h

CM||DBDBMC- =>DC=BM

ACM-. (AC=d2; CM=d1; AM=a+b)

d1+d2=AMd1+d2=(a+b) d1=a+h ( ADB) d2=h+b ( ADC) a+h+h+b==a+2ab+b2h=2abh=ab