Răspunsuri

2014-05-13T19:32:56+03:00
ABCD trapezul, DE, CF inaltimile, BC=AD=10 (trapezul isos arelat neparalele congruente)
 AE=FB=(20-8)/2=6
ΔCFB Δ dreptunghi BC²=FB²+CF²⇒CF²=BC²-FB²=100-36=64⇒CF=8
A=(AB+CD)xCF/2=(20+8)8/2=112